[
{
"id": "authors:3qy60-wkc35",
"collection": "authors",
"collection_id": "3qy60-wkc35",
"cite_using_url": "https://authors.library.caltech.edu/records/3qy60-wkc35",
"type": "article",
"title": "Relativistic Magnetohydrodynamic Simulations of Giant Magnetar Bursts",
"author": [
{
"family_name": "Chatterjee",
"given_name": "Koushik",
"orcid": "0000-0002-2825-3590"
},
{
"family_name": "Philippov",
"given_name": "Alexander",
"orcid": "0000-0001-7801-0362"
},
{
"family_name": "Beloborodov",
"given_name": "Andrei M.",
"orcid": "0000-0001-5660-3175"
},
{
"family_name": "Parfrey",
"given_name": "Kyle",
"orcid": "0000-0001-6173-0099"
},
{
"family_name": "Ripperda",
"given_name": "Bart",
"orcid": "0000-0002-7301-3908"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "\n
Gradual crustal deformation can generate strongly twisted magnetic fields around magnetars, potentially triggering giant flares with total energies exceeding 1044 erg. In this letter, we present the first relativistic magnetohydrodynamic simulation of a surface shear-driven magnetar eruption, capturing reconnection-driven plasma heating, the ejection of relativistically hot plasma, and the formation of a hot fireball confined within the inner magnetosphere. We find that magnetic reconnection in the equatorial current sheet launches a hot trailing outflow capable of powering the initial spike observed in giant flares, while simultaneously leaving behind a thermally stratified fireball with sufficient thermal energy to produce the pulsating, decaying tail. Together, these features provide a self-consistent physical framework for understanding the observed energetics of magnetar giant flares. The eruption also expels a magnetically dominated giant plasmoid carrying up to ∼9% of the magnetosphere’s total magnetic energy. Furthermore, our simulation demonstrates how the plasmoid drives the formation of a blast wave—an important ingredient in models linking magnetar eruptions to fast radio bursts.
\n
Waves launched from the neutron star surface or inner magnetosphere propagate through the magnetosphere as small perturbations, but can grow relative to the background magnetic field and steepen into \"monster shocks\"—ultrarelativistic magnetized shocks that can power high-energy emission. Such shocks can develop around isolated magnetars, merging binaries, and collapsing neutron stars. They occur in magnetically dominated plasma and are described by relativistic magnetohydrodynamics (MHD). We present global relativistic MHD simulations of monster shocks in unperturbed and perturbed (\"wrinkled\") backgrounds with a global dipolar geometry. Our simulations confirm analytical predictions for equatorial shocks and provide new insight into the behavior of oblique shocks off the equator. Simulations where the shock is formed through Alfvén mode to fast mode conversion are also presented, demonstrating the generic nature of the monster shock mechanism. We explore how the presence of additional modes in the magnetosphere modifies the shock behavior. Modes of comparable amplitude can fragment the shock front, substantially reduce the magnetization, produce localized enhancements in the Lorentz factor relative to an unperturbed dipole background, and intermittently generate additional shocks along a line of sight.
",
"doi": "10.3847/1538-4357/ae633a",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-07-10",
"series_number": "2",
"volume": "1005",
"issue": "2",
"pages": "158"
},
{
"id": "authors:qfm2c-0py36",
"collection": "authors",
"collection_id": "qfm2c-0py36",
"cite_using_url": "https://authors.library.caltech.edu/records/qfm2c-0py36",
"type": "article",
"title": "Error quantification and comparison of binary neutron star gravitational waveforms from numerical relativity codes",
"author": [
{
"family_name": "Habib",
"given_name": "Sarah",
"orcid": "0000-0002-4725-4978",
"clpid": "Habib-Sarah"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Deppe",
"given_name": "Nils",
"orcid": "0000-0003-4557-4115"
},
{
"family_name": "Foucart",
"given_name": "Francois",
"orcid": "0000-0003-4617-4738"
},
{
"family_name": "Scheel",
"given_name": "Mark A.",
"orcid": "0000-0001-6656-9134",
"clpid": "Scheel-M-A"
},
{
"family_name": "Teukolsky",
"given_name": "Saul",
"orcid": "0000-0001-9765-4526",
"clpid": "Teukolsky-S-A"
},
{
"family_name": "Boyle",
"given_name": "Michael"
},
{
"family_name": "Duez",
"given_name": "Matthew",
"orcid": "0000-0002-0050-1783"
},
{
"family_name": "Kidder",
"given_name": "Larry",
"orcid": "0000-0001-5392-7342"
},
{
"family_name": "Moxon",
"given_name": "Jordan",
"orcid": "0000-0001-9891-8677",
"clpid": "Moxon-Jordan"
},
{
"family_name": "Nelli",
"given_name": "Kyle C.",
"orcid": "0000-0003-2426-8768",
"clpid": "Nelli-Kyle-C"
},
{
"family_name": "Pfeiffer",
"given_name": "Harald",
"orcid": "0000-0001-9288-519X"
},
{
"family_name": "Throwe",
"given_name": "William",
"orcid": "0000-0001-5059-4378"
},
{
"family_name": "Vu",
"given_name": "Nils",
"orcid": "0000-0002-5767-3949",
"clpid": "Vu-Nils"
}
],
"abstract": "Future gravitational wave detections of merging binary neutron star systems have the possibility to tightly constrain the equation of state of dense nuclear matter. In order to extract such constraints, gravitational waveform models need to be calibrated to accurate numerical relativity simulations of the late inspiral and merger. In this work, we take an essential step toward classifying the error and potential systematics in current generation numerical relativity simulations of merging binary neutron stars. To this end, we perform a direct comparison of two codes (fil, spec), which differ in many aspects, including the numerical methods and discretizations used and equations solved. We find that despite these different approaches, the codes are—within current numerical resolution bounds—fully consistent, and broadly comparable in cost for a given accuracy level. Our results indicate that the error in the waveforms is primarily dominated by the hydrodynamic evolution, consistent with earlier findings in the literature. We also discuss current limitations and cost estimates for numerical relativity simulations to reach the accuracies required in the era of next-generation gravitational detectors.
",
"doi": "10.1103/5sxn-knwz",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2026-05-28",
"series_number": "10",
"volume": "113",
"issue": "10",
"pages": "104062"
},
{
"id": "authors:s721w-n7m27",
"collection": "authors",
"collection_id": "s721w-n7m27",
"cite_using_url": "https://authors.library.caltech.edu/records/s721w-n7m27",
"type": "article",
"title": "Relativistic scalar dark matter drag forces on a black hole binary",
"author": [
{
"family_name": "Xin",
"given_name": "Shuo",
"orcid": "0000-0002-6062-4849"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "Dark matter around black holes can induce drag forces through dynamical friction and accretion, potentially affecting the orbital evolution and gravitational wave emission of binary systems. We here present a series of two-dimensional general relativistic simulations of a black hole binary in a wind tunnel for an asymptotically homogeneous scalar field background. We extract the drag forces, torque, mass and charge accretion acting on the binary, and analyze their dependence on the binary separation, velocity and the scalar field parameters. We find that the binary’s drag is not a simple superposition of two isolated black holes; the presence of a companion modifies the gravitational wake and yields significant nonlinearities. This additional force and torque can (in principle) modify the inspiral and induce a dephasing of the gravitational wave signal.
",
"doi": "10.1103/wgjx-qpdw",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2026-05-19",
"series_number": "10",
"volume": "113",
"issue": "10",
"pages": "103032"
},
{
"id": "authors:dxent-z4z57",
"collection": "authors",
"collection_id": "dxent-z4z57",
"cite_using_url": "https://authors.library.caltech.edu/records/dxent-z4z57",
"type": "article",
"title": "Unraveling the Emission Mechanism Powering Long Period Radio Transients from Interacting White Dwarf Binaries via Kinetic Plasma Simulations",
"author": [
{
"family_name": "Zhong",
"given_name": "Yici",
"orcid": "0000-0003-0805-8234",
"clpid": "Zhong-Yici"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "Recent observations of long period radio transients, such as GLEAM-X J0704–37 and ILT J1101+5521, have revealed a previously unrecognized population of Galactic radio transient sources associated with white dwarf (WD)–M dwarf (MD) binaries. It is an open question how to produce coherent radio emission in these systems, though a model driven by binary interaction seems likely given the nature and correlation of the emission with the binaries' orbital period. Using kinetic plasma simulations, we demonstrate that the relativistic electron cyclotron maser instability (ECMI) is a viable mechanism for generating radio pulses in WD–MD systems, akin to planetary radio emission, such as that from the Jupiter–Io system. We quantify the relativistic ECMI in the nonlinear regime under conditions relevant for WD radio emission for the first time. Our simulations demonstrate that the ECMI can intrinsically produce partially linearly polarized emission relevant to explaining the observed emission spectra of two Galactic sources, though the precise details will depend on the plasma composition. Our work paves the way for a systematic and fully nonlinear computational modeling of radio emission from interacting WD sources.
",
"doi": "10.3847/2041-8213/ae4337",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2026-03-01",
"series_number": "1",
"volume": "999",
"issue": "1",
"pages": "L2"
},
{
"id": "authors:k10cy-nf777",
"collection": "authors",
"collection_id": "k10cy-nf777",
"cite_using_url": "https://authors.library.caltech.edu/records/k10cy-nf777",
"type": "article",
"title": "AthenaK: A Performance-portable Version of the Athena++ Adaptive Mesh Refinement Framework",
"author": [
{
"family_name": "Stone",
"given_name": "James M.",
"orcid": "0000-0001-5603-1832"
},
{
"family_name": "Mullen",
"given_name": "Patrick D.",
"orcid": "0000-0003-2131-4634"
},
{
"family_name": "Fielding",
"given_name": "Drummond",
"orcid": "0000-0003-3806-8548"
},
{
"family_name": "Grete",
"given_name": "Philipp",
"orcid": "0000-0003-3555-9886"
},
{
"family_name": "Guo \u90ed",
"given_name": "Minghao \u660e\u6d69",
"orcid": "0000-0002-3680-5420"
},
{
"family_name": "Kempski",
"given_name": "Philipp",
"orcid": "0009-0009-2144-3912"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "White",
"given_name": "Christopher J."
},
{
"family_name": "Wong",
"given_name": "George N.",
"orcid": "0000-0001-6952-2147"
}
],
"abstract": "We describe AthenaK : a new implementation of the Athena++ block-based adaptive mesh refinement framework using the Kokkos programming model. Finite volume methods for Newtonian, special relativistic, and general relativistic (GR) hydrodynamics and magnetohydrodynamics (MHD), and GR-radiation hydrodynamics and MHD, as well as a module for evolving Lagrangian tracer or charged test particles (e.g., cosmic rays) are implemented using the framework. In two companion papers, we describe (1) a new solver for the Einstein equations based on the Z4c formalism, and (2) a GRMHD solver in dynamical spacetimes also implemented using the framework, enabling new applications in numerical relativity. By adopting Kokkos , the code can be run on virtually any hardware, including CPUs, GPUs from multiple vendors, and emerging Advanced RISC Machine processors. AthenaK shows excellent performance and weak scaling, achieving over 1 billion cell updates per second for hydrodynamics in three dimensions on a single NVIDIA Grace Hopper processor. It does this with a typical parallel efficiency of 80% on 65,536 AMD GPUs on the OLCF Frontier system. Such performance portability enables AthenaK to leverage modern exascale computing systems for challenging applications in astrophysical fluid dynamics, numerical relativity, and multimessenger astrophysics.
",
"doi": "10.3847/1538-4365/ae3717",
"issn": "0067-0049",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Supplement Series",
"publication_date": "2026-03",
"series_number": "1",
"volume": "283",
"issue": "1",
"pages": "27"
},
{
"id": "authors:tfd9x-ns971",
"collection": "authors",
"collection_id": "tfd9x-ns971",
"cite_using_url": "https://authors.library.caltech.edu/records/tfd9x-ns971",
"type": "article",
"title": "The Atacama Cosmology Telescope: Observations of supermassive black hole binary candidates. Strong sinusoidal variations at 95, 147, and 225 GHz in PKS 2131\u2013021 and PKS J0805\u20130111",
"author": [
{
"family_name": "Hincks",
"given_name": "Adam D.",
"orcid": "0000-0003-1690-6678"
},
{
"family_name": "Ma",
"given_name": "Xiaoyi"
},
{
"family_name": "Mr\u00f3z",
"given_name": "Przemek",
"orcid": "0000-0001-7016-1692"
},
{
"family_name": "Naess",
"given_name": "Sigurd K.",
"orcid": "0000-0002-4478-7111"
},
{
"family_name": "Kiehlmann",
"given_name": "Sebastian",
"orcid": "0000-0001-6314-9177"
},
{
"family_name": "Blandford",
"given_name": "Roger D.",
"orcid": "0000-0002-1854-5506",
"clpid": "Blandford-R-D"
},
{
"family_name": "Bond",
"given_name": "J. Richard",
"orcid": "0000-0003-2358-9949"
},
{
"family_name": "Devlin",
"given_name": "Mark",
"orcid": "0000-0002-3169-9761"
},
{
"family_name": "Dunkley",
"given_name": "Jo",
"orcid": "0000-0002-7450-2586"
},
{
"family_name": "Foster",
"given_name": "Allen",
"orcid": "0000-0002-7145-1824"
},
{
"family_name": "Graham",
"given_name": "Matthew J.",
"orcid": "0000-0002-3168-0139",
"clpid": "Graham-M-J"
},
{
"family_name": "Guan",
"given_name": "Yilun"
},
{
"family_name": "Herv\u00edas-Caimapo",
"given_name": "Carlos",
"orcid": "0000-0002-4765-3426"
},
{
"family_name": "Hood",
"given_name": "John C.",
"orcid": "0000-0003-4157-4185"
},
{
"family_name": "Kosowsky",
"given_name": "Arthur",
"orcid": "0000-0002-3734-331X"
},
{
"family_name": "Lalakos",
"given_name": "Aretaios",
"orcid": "0000-0002-6883-6520",
"clpid": "Lalakos-Aretaios"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Niemack",
"given_name": "Michael D.",
"orcid": "0000-0001-7125-3580"
},
{
"family_name": "Orlowski-Scherer",
"given_name": "John",
"orcid": "0000-0003-1842-8104"
},
{
"family_name": "Page",
"given_name": "Lyman A.",
"orcid": "0000-0002-9828-3525"
},
{
"family_name": "Partridge",
"given_name": "Bruce",
"orcid": "0000-0001-6541-9265"
},
{
"family_name": "Readhead",
"given_name": "Anthony C. S.",
"orcid": "0000-0001-9152-961X",
"clpid": "Readhead-A-C-S"
},
{
"family_name": "Sif\u00f3n",
"given_name": "Crist\u00f3bal",
"orcid": "0000-0002-8149-1352"
},
{
"family_name": "Staggs",
"given_name": "Suzanne T.",
"orcid": "0000-0002-7020-7301"
},
{
"family_name": "Sullivan",
"given_name": "Andrew G.",
"orcid": "0000-0002-9545-7286"
},
{
"family_name": "Vargas",
"given_name": "Cristian",
"orcid": "0000-0001-5327-1400"
}
],
"abstract": "Large sinusoidal variations in the radio light curves of the blazars PKS J0805–0111 and PKS 2131–021 have recently been discovered with an 18-year monitoring programme at the Owens Valley Radio Observatory, making these systems strong supermassive black hole binary (SMBHB) candidates. The sinusoidal variations in PKS 2131–021 dominate its light curves from 2.7 GHz to optical frequencies. We report sinusoidal variations observed in both objects with the Atacama Cosmology Telescope (ACT) at 95, 147, and 225 GHz consistent with the radio light curves. The ACT 95 GHz light curve of PKS 2131–021 agrees well with the contemporaneous 91.5 GHz ALMA light curve and is comparable in quality, while the ACT light curves of PKS J0805–0111, for which there are no ALMA or other millimetre light curves, show that PKS 2131–021 is not an isolated case, and that this class of AGN exhibits the following properties: (a) the sinusoidal pattern dominates over a broad range of frequencies; (b) the amplitude of the sine wave compared to its mean value is monochromatic (i.e. nearly constant across frequencies); (c) the phase of the sinusoid phase changes monotonically as a function of frequency; (d) the sinusoidal variations are intermittent. We describe a physical model for SMBHB systems, the modified Kinetic Orbital model, that explains all four of these phenomena. The monitoring of ∼8000 blazars by the Simons Observatory over the next decade should provide a large number of SMBHB candidates that will shed light on the nature of the nanohertz gravitational-wave background.
",
"doi": "10.1051/0004-6361/202555047",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2026-02",
"volume": "706",
"pages": "A206"
},
{
"id": "authors:8k50w-pqv87",
"collection": "authors",
"collection_id": "8k50w-pqv87",
"cite_using_url": "https://authors.library.caltech.edu/records/8k50w-pqv87",
"type": "article",
"title": "Compelling Evidence for a Harmonic in the Light Curve of the Supermassive Black Hole Binary Candidate PKS J1309+1154",
"author": [
{
"family_name": "Readhead",
"given_name": "A. C. S.",
"orcid": "0000-0001-9152-961X",
"clpid": "Readhead-A-C-S"
},
{
"family_name": "Aller",
"given_name": "M. F.",
"orcid": "0000-0003-2483-2103"
},
{
"family_name": "Sullivan",
"given_name": "A. G.",
"orcid": "0000-0002-9545-7286"
},
{
"family_name": "Blandford",
"given_name": "R. D.",
"orcid": "0000-0002-1854-5506",
"clpid": "Blandford-R-D"
},
{
"family_name": "Mr\u00f3z",
"given_name": "P.",
"orcid": "0000-0001-7016-1692"
},
{
"family_name": "De la Parra",
"given_name": "P. V.",
"orcid": "0000-0001-5957-1412"
},
{
"family_name": "Molina",
"given_name": "B.",
"orcid": "0009-0000-9963-6874"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Lister",
"given_name": "M. L.",
"orcid": "0000-0003-1315-3412"
},
{
"family_name": "Synani",
"given_name": "A.",
"orcid": "0009-0004-2614-830X"
},
{
"family_name": "Aller",
"given_name": "H.",
"orcid": "0000-0003-1945-1840"
},
{
"family_name": "Begelman",
"given_name": "M. C.",
"orcid": "0000-0003-0936-8488"
},
{
"family_name": "Ding",
"given_name": "Y.",
"orcid": "0000-0002-5770-2666",
"clpid": "Ding-Yuanze"
},
{
"family_name": "Graham",
"given_name": "M. J.",
"orcid": "0000-0002-3168-0139",
"clpid": "Graham-M-J"
},
{
"family_name": "Harrison",
"given_name": "F.",
"orcid": "0000-0002-4226-8959",
"clpid": "Harrison-F-A"
},
{
"family_name": "Hovatta",
"given_name": "T.",
"orcid": "0000-0002-2024-8199"
},
{
"family_name": "Liodakis",
"given_name": "I.",
"orcid": "0000-0001-9200-4006"
},
{
"family_name": "Max-Moerbeck",
"given_name": "W.",
"orcid": "0000-0002-5491-5244"
},
{
"family_name": "Pavlidou",
"given_name": "V.",
"orcid": "0000-0002-0870-1368"
},
{
"family_name": "Pearson",
"given_name": "T. J.",
"orcid": "0000-0001-5213-6231",
"clpid": "Pearson-T-J"
},
{
"family_name": "Ravi",
"given_name": "V.",
"orcid": "0000-0002-7252-5485",
"clpid": "Ravi-Vikram"
},
{
"family_name": "Reeves",
"given_name": "R. A.",
"orcid": "0000-0001-5704-271X"
},
{
"family_name": "Surti",
"given_name": "T.",
"orcid": "0000-0002-6369-6266",
"clpid": "Surti-Tirth"
},
{
"family_name": "Tassis",
"given_name": "K.",
"orcid": "0000-0002-8831-2038"
},
{
"family_name": "Tremblay",
"given_name": "S. E.",
"orcid": "0000-0001-7662-2576"
},
{
"family_name": "Zensus",
"given_name": "J. A.",
"orcid": "0000-0001-7470-3321"
}
],
"abstract": "We recently discovered a supermassive black hole binary (SMBHB) candidate, PKS J1309+1154, in the combined 46 yr University of Michigan Radio Astronomy Observatory (UMRAO) plus Owens Valley Radio Observatory (OVRO) blazar monitoring programs at 14.5/15 GHz. The light curve of PKS 1309+1154 exhibits a 17.9 yr periodicity. We also reported a hint of a first harmonic with a 9 yr periodicity in this object. Further analysis of the PKS J1309+1154 light curve provides compelling evidence that both the fundamental and the harmonic are real, confirming the existence of real periodicities in blazar light curves. This is the first case, to our knowledge, of watertight evidence for a fundamental periodicity and a harmonic periodicity in a blazar light curve. It makes PKS J1309+1154 a strong SMBHB candidate and thus the third such candidate to be revealed through long-term radio monitoring, the other two being PKS J0805–0111 and PKS 2131–021, both discovered through the OVRO 40 m Telescope monitoring program. It is argued that hundreds of SMBHB candidates will be discovered by the combination of the South Pole Telescope, the Vera Rubin Observatory, and the Simons Observatory. Coherent searches for gravitational waves from a network of SMBHB candidates, starting immediately, are strongly motivated.
",
"doi": "10.3847/2041-8213/ae2656",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2026-01-10",
"series_number": "2",
"volume": "996",
"issue": "2",
"pages": "L39"
},
{
"id": "authors:zbpph-gjp83",
"collection": "authors",
"collection_id": "zbpph-gjp83",
"cite_using_url": "https://authors.library.caltech.edu/records/zbpph-gjp83",
"type": "article",
"title": "Validity of a finite temperature expansion for dense nuclear matter",
"author": [
{
"family_name": "Mroczek",
"given_name": "Debora"
},
{
"family_name": "Yao",
"given_name": "Nanxi",
"orcid": "0009-0004-7270-4346"
},
{
"family_name": "Zine",
"given_name": "Katherine",
"orcid": "0000-0002-1095-3812"
},
{
"family_name": "Noronha-Hostler",
"given_name": "Jacquelyn",
"orcid": "0000-0003-3229-4958"
},
{
"family_name": "Brodie",
"given_name": "Liam",
"orcid": "0000-0001-7708-2073"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626"
},
{
"family_name": "Haber",
"given_name": "Alexander",
"orcid": "0000-0002-5511-9565"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "In this work we provide a new, well-controlled expansion of the equation of state of dense matter from zero to finite temperatures (\ud835\udc47) while covering a wide range of charge fractions (\ud835\udc4c\ud835\udc44), from pure neutron to isospin symmetric nuclear matter. Our expansion can be used to describe neutron star mergers using the equation of state inferred from neutron star observations. We discuss how knowledge from low-energy nuclear experiments and heavy-ion collisions can be directly incorporated into the expansion. We also suggest new thermodynamic quantities of interest that can be calculated from theoretical models or directly inferred by experimental data that can be used to infer the finite temperature equation of state. With our new method, we can quantify the uncertainty in our finite \ud835\udc47 and \ud835\udc4c\ud835\udc44 expansions without making assumptions about the underlying degrees of freedom. We can reproduce results from a microscopic equation of state up to \ud835\udc47=100 MeV for baryon chemical potential \ud835\udf07\ud835\udc35 \u2273 1100 MeV [≈(1–2)\u2062\ud835\udc5bsat] within 5% error, with even better results for larger \ud835\udf07\ud835\udc35 and/or lower \ud835\udc47. We investigate the sources of numerical and theoretical uncertainty and discuss future directions of study.
",
"doi": "10.1103/y8tw-m4sz",
"issn": "2469-9985",
"publisher": "American Physical Society",
"publication": "Physical Review C",
"publication_date": "2026-01-09",
"series_number": "1",
"volume": "113",
"issue": "1",
"pages": "015804"
},
{
"id": "authors:2trnv-m6j85",
"collection": "authors",
"collection_id": "2trnv-m6j85",
"cite_using_url": "https://authors.library.caltech.edu/records/2trnv-m6j85",
"type": "article",
"title": "Universal radial scaling of large-scale black hole accretion for magnetically arrested and rocking accretion disks",
"author": [
{
"family_name": "Lalakos",
"given_name": "Aretaios",
"orcid": "0000-0002-6883-6520",
"clpid": "Lalakos-Aretaios"
},
{
"family_name": "Tchekhovskoy",
"given_name": "Alexander",
"orcid": "0000-0002-9182-2047"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Ripperda",
"given_name": "Bart",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Bart"
},
{
"family_name": "Chatterjee",
"given_name": "Koushik"
},
{
"family_name": "Liska",
"given_name": "Matthew",
"orcid": "0000-0003-4475-9345"
}
],
"abstract": "Accretion onto supermassive black holes (BHs) can launch relativistic outflows and jets that inject energy and momentum into their surroundings. Understanding how such feedback shapes large-scale accretion is key to bridging observations from galactic scales (e.g., the Bondi radius, \ud835\udc5fB) down to event horizon scales (\ud835\udc5fg), spanning five to six orders of magnitude. To address this challenge directly, we treat the spatial scale separation as a free parameter, varying it across two to four orders of magnitude. We perform a suite of the longest contiguous 3D general relativistic magnetohydrodynamic simulations to date (\ud835\udc61≤4×10\u2076\ud835\udc5fg/\ud835\udc50), modeling Bondi-like accretion of rotating, nonrelativistic gas with weak vertical magnetic fields onto a rapidly spinning BH, achieving inflow equilibrium out to \ud835\udc5f\u227310³\u2062\ud835\udc5fg. We find that, regardless of scale separation or ambient gas rotation, all simulations reach a magnetically arrested disk (MAD) state in which the BH becomes magnetically saturated. In this state, the mass inflow rate follows a universal radial scaling relative to the Bondi rate: \u02d9\ud835\udc40in\u2061(\ud835\udc5f)/\u02d9\ud835\udc40B ∼(\ud835\udc5f/\ud835\udc5fB)\ud835\udc60 with \ud835\udc60 =0.66 ±0.03. The MAD state self-regulates through jets, outflows, and magnetic flux eruptions that can ultimately disrupt coherent angular momentum inflow, giving rise to a rocking accretion disk (RAD) state. This RAD state features chaotically oriented inflows, weak intermittent jets, and a steeper inflow slope of \ud835\udc60 =0.87 ±0.05, along with significantly weaker outflows. For rapidly spinning BHs, the MAD and RAD BH accretion rates become comparable at typical scale separations, \ud835\udc5fB/\ud835\udc5fg \u227310\u2075. The weaker outflows in the RAD state allow large-scale inflows to resume, eventually restoring the MAD state and enabling a repeating MAD-RAD cycle. We find that the MAD-RAD timescales can last from a few to hundreds of Bondi timescales, \ud835\udc61B ∼0.2 Myr ×(\ud835\udc5fB/10\u2075\u2062\ud835\udc5fg^(3/2) ×(\ud835\udc40BH/10\u2079\ud835\udc40\u2299), where \ud835\udc40BH is the BH mass, potentially setting the duty cycle of jetted active galactic nucleus outbursts, like M87*.
",
"doi": "10.1103/zkq5-bj75",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2025-12-26",
"series_number": "12",
"volume": "112",
"issue": "12",
"pages": "123044"
},
{
"id": "authors:dmca9-b2t74",
"collection": "authors",
"collection_id": "dmca9-b2t74",
"cite_using_url": "https://authors.library.caltech.edu/records/dmca9-b2t74",
"type": "article",
"title": "Crustal Quakes Spark Magnetospheric Blasts: Imprints of Realistic Magnetar Crust Oscillations on the Fast Radio Burst Signal",
"author": [
{
"family_name": "Burnaz",
"given_name": "Louis",
"orcid": "0009-0006-2620-0328",
"clpid": "Burnaz-Louis"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Bransgrove",
"given_name": "Ashley",
"orcid": "0000-0002-9711-9424"
}
],
"abstract": "Many transients believed to originate from magnetars are thought to be triggered by crustal activity, which feeds back on the surrounding magnetosphere. These perturbations, through a variety of proposed mechanisms, can convert a fraction of the magnetic energy stored in the magnetosphere, as well as the energy injected by crustal activity itself into electromagnetic emission, including X-ray bursts and fast radio bursts. We here provide a first glimpse of this process by coupling magnetoelastic dynamics simulations of the crust to fully three-dimensional relativistic resistive force-free electrodynamic simulations of the magnetosphere. Our simulations demonstrate that the elastodynamical motions of the surface launch a series of fast magnetosonic and Alfvén waves into the magnetosphere. These waves rapidly enter a nonlinear regime, ultimately giving rise to a wide range of phenomena, including monster shock formation, relativistic blast waves, trapped Alfvén waves, nonlinear Alfvén wave ejecta, and transient equatorial current sheets interacting with these waves. After the initial nonlinear phase, the magnetosphere is partially combed out, resembling a strongly perturbed split monopole configuration. Our results can offer hints and potential constraints on fast radio burst emission mechanisms, in particular for hyperactive repeating sources, by placing tight bounds on energy conversion efficiency and possible quasiperiodic imprints on magnetospheric waves by elastic oscillations of the crust.
",
"doi": "10.3847/2041-8213/ae2466",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2025-12-20",
"series_number": "2",
"volume": "995",
"issue": "2",
"pages": "L57"
},
{
"id": "authors:te951-d8c73",
"collection": "authors",
"collection_id": "te951-d8c73",
"cite_using_url": "https://authors.library.caltech.edu/records/te951-d8c73",
"type": "article",
"title": "Unveiling the Electrodynamic Nature of Spacetime Collisions",
"author": [
{
"family_name": "Boyeneni",
"given_name": "Siddharth",
"orcid": "0009-0000-7589-9602",
"clpid": "Boyeneni-Siddharth"
},
{
"family_name": "Wu",
"given_name": "Jiaxi",
"orcid": "0000-0003-3829-967X",
"clpid": "Wu-Jiaxi"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "Gravitational waves from merging binary black holes present exciting opportunities for understanding fundamental aspects of gravity, including nonlinearities in the strong-field regime. One challenge in studying and interpreting the dynamics of binary black hole collisions is the intrinsically geometrical nature of spacetime, which in many ways is unlike that of other classical field theories. By exactly recasting Einstein’s equations into a set of coupled nonlinear Maxwell equations closely resembling classical electrodynamics, we visualize the intricate dynamics of gravitational electric and magnetic fields during the inspiral, merger, and ringdown of a binary black hole collision.
",
"doi": "10.1103/995s-wxl7",
"issn": "0031-9007",
"publisher": "American Physical Society",
"publication": "Physical Review Letters",
"publication_date": "2025-09-02",
"series_number": "10",
"volume": "135",
"issue": "10",
"pages": "101401"
},
{
"id": "authors:ffn61-5za20",
"collection": "authors",
"collection_id": "ffn61-5za20",
"cite_using_url": "https://authors.library.caltech.edu/records/ffn61-5za20",
"type": "article",
"title": "Impact of Magnetic-field-driven Anisotropies on the Equation of State Probed in Neutron Star Mergers",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Peterson",
"given_name": "Jeffrey",
"orcid": "0000-0002-6703-418X"
},
{
"family_name": "Scurto",
"given_name": "Luigi",
"orcid": "0000-0002-8763-5660"
},
{
"family_name": "Pais",
"given_name": "Helena",
"orcid": "0000-0001-7247-1950"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626"
}
],
"abstract": "Binary neutron star mergers can produce extreme magnetic fields, some of which can lead to strong magnetar-like remnants. While strong magnetic fields have been shown to affect the dynamics of outflows and angular momentum transport in the remnant, they can also crucially alter the properties of nuclear matter probed in the merger. In this work, we provide a first assessment of the latter, determining the strength of the pressure anisotropy caused by Landau-level quantization and the anomalous magnetic moment. To this end, we perform the first numerical relativity simulation with a magnetic polarization tensor and a magnetic-field-dependent equation of state using a new algorithm we present here, which also incorporates a mean-field dynamo model to control the magnetic field strength present in the merger remnant. Our results show that—in the most optimistic case—corrections to the anisotropy can be in excess of 10% and are potentially largest in the outer layers of the remnant. This work paves the way for a systematic investigation of these effects.
",
"doi": "10.3847/2041-8213/adf62d",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2025-08-20",
"series_number": "2",
"volume": "989",
"issue": "2",
"pages": "L29"
},
{
"id": "authors:apz20-6b931",
"collection": "authors",
"collection_id": "apz20-6b931",
"cite_using_url": "https://authors.library.caltech.edu/records/apz20-6b931",
"type": "article",
"title": "On the Impact of Neutrinos on the Launching of Relativistic Jets from \"Magnetars\" Produced in Neutron Star Mergers",
"author": [
{
"family_name": "Musolino",
"given_name": "Carlo",
"orcid": "0000-0002-9955-3451"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103"
},
{
"family_name": "Most",
"given_name": "Elias",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "\n
A significant interest has emerged recently in assessing whether collimated and ultrarelativistic outflows can be produced by a long-lived remnant from a binary neutron star (BNS) merger, with different approaches leading to different outcomes. To clarify some of the aspect of this process, we report the results of long-term (i.e., ∼110 ms) state-of-the-art general relativistic magnetohydrodynamics simulations of the inspiral and merger of a BNS system of magnetized stars. We find that after ∼50 ms from the merger an α–Ω dynamo driven by the magnetorotational instability sets in in the densest regions of the disk and leads to the breakout of the magnetic field lines from the accretion disk around the remnant. The breakout is responsible for generating a collimated, magnetically driven outflow with only mildly relativistic velocities and for a violent eruption of electromagnetic energy. We provide evidence that this outflow is partly collimated via a Blandford–Payne mechanism. Finally, by including or not the radiative transport via neutrinos, we determine the role they play in the launching of the collimated wind. In this way, we conclude that the mechanism of magnetic field breakout we observe is robust and takes place even without neutrinos. Contrary to previous expectations, the inclusion of neutrino absorption and emission leads to a smaller baryon pollution in polar regions and hence accelerates the occurrence of the breakout, yielding a larger electromagnetic luminosity. Given the mildly relativistic nature of these disk-driven breakout outflows, it is difficult to consider them responsible for the jet phenomenology observed in short gamma-ray bursts.
\n
The dynamics of a black hole traveling through a plasma—a general relativistic extension of the classic Bondi-Hoyle-Lyttleton (BHL) accretion problem—can be related to a variety of astrophysical contexts, including the aftermath of binary black hole mergers in gaseous environments. We perform three-dimensional general relativistic magnetohydrodynamics simulations of BHL accretion onto a spinning black hole when magnetic field of the incoming wind is inclined to the spin axis of the black hole. Irrespective of inclination but dependent on the wind speed, we find that the accretion flow onto the black hole can become magnetically arrested, launching an intermittent jet whose formation is assisted by a turbulent dynamolike process in the inner disk. The upstream ram pressure of the wind bends the jet, and confines the angular extent into which the magnetic flux tubes ejected from quasiperiodic eruptions are released. Recoil from magnetic flux eruptions drives strong oscillations in the inner accretion disk, resulting in jet nutation at the outer radii and occasionally ripping off the inner part of the accretion disk. When the incoming magnetic field is perpendicular to the spin axis of the black hole, we find that the magnetic polarity of the jets can undergo a stochastic reversal. In addition to dynamical friction, the black hole experiences a perpendicular drag force analogous to the Magnus effect. Qualitative effects of the incoming magnetic field orientation, the strength of the magnetization, and the incoming wind speed are investigated as well.
",
"doi": "10.1103/physrevd.111.083025",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2025-04-16",
"series_number": "8",
"volume": "111",
"issue": "8",
"pages": "083025"
},
{
"id": "authors:fytdw-e3y97",
"collection": "authors",
"collection_id": "fytdw-e3y97",
"cite_using_url": "https://authors.library.caltech.edu/records/fytdw-e3y97",
"type": "article",
"title": "Decoupling of a supermassive black hole binary from its magnetically arrested circumbinary accretion disk",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Wang",
"given_name": "Hai-Yang",
"orcid": "0000-0001-7167-6110",
"clpid": "Wang-Hai-Yang"
}
],
"abstract": "Merging supermassive black hole (SMBH) binaries will likely be surrounded by a circumbinary accretion disk. Close to merger, a gravitational radiation-driven inspiral will happen on timescales faster than the effective viscous time at the disk cavity wall, leading to a decoupling of the inner binary dynamics from the surrounding gaseous environment. Here we perform the first magnetohydrodynamics simulation of this decoupling process from a magnetically arrested circumbinary accretion disk. In this regime, the central cavity is filled with a very strong vertical magnetic flux, regulating accretion onto the binary. Our simulations identify three main stages of this process: (i) large-scale magnetic flux loss prior to decoupling, (ii) Rayleigh-Taylor-driven accretion streams onto the binary during and after decoupling, which can power magnetic towerlike outflows, resembling dual jets, and (iii) postmerger, the cavity wall becomes unstable and the magnetic flux trapped inside the cavity will get ejected in large coherent outbreak episodes with implications for potential multimessenger transients to merging SMBH binaries.
",
"doi": "10.1103/PhysRevD.111.L081304",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2025-04-15",
"series_number": "8",
"volume": "111",
"issue": "8",
"pages": "L081304"
},
{
"id": "authors:ynwcy-kxn88",
"collection": "authors",
"collection_id": "ynwcy-kxn88",
"cite_using_url": "https://authors.library.caltech.edu/records/ynwcy-kxn88",
"type": "article",
"title": "Black Hole Pulsars and Monster Shocks as Outcomes of Black Hole\u2013Neutron Star Mergers",
"author": [
{
"family_name": "Kim",
"given_name": "Yoonsoo",
"orcid": "0000-0002-4305-6026",
"clpid": "Kim-Yonsoo"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Beloborodov",
"given_name": "Andrei M.",
"orcid": "0000-0001-5660-3175",
"clpid": "Beloborodov-Andrei-M"
},
{
"family_name": "Ripperda",
"given_name": "Bart",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Bart"
}
],
"abstract": "\n
The merger of a black hole (BH) and a neutron star (NS) in most cases is expected to leave no material around the remnant BH; therefore, such events are often considered as sources of gravitational waves without electromagnetic counterparts. However, a bright counterpart can emerge if the NS is strongly magnetized, as its external magnetosphere can experience radiative shocks and magnetic reconnection during/after the merger. We use magnetohydrodynamic simulations in the dynamical spacetime of a merging BH–NS binary to investigate its magnetospheric dynamics. We find that compressive waves excited in the magnetosphere develop into monster shocks as they propagate outward. After swallowing the NS, the BH acquires a magnetosphere that quickly evolves into a split-monopole configuration and then undergoes an exponential decay (balding), enabled by magnetic reconnection and also assisted by the ringdown of the remnant BH. This spinning BH drags the split monopole into rotation, forming a transient pulsar-like state. It emits a striped wind if the swallowed magnetic-dipole moment is inclined to the spin axis. We predict two types of transients from this scenario: (1) a fast radio burst emitted by the shocks as they expand to large radii; and (2) an X-ray/γ-ray burst emitted by the e± outflow heated by magnetic dissipation.
\n
Black holes threaded by massive vector fields can be subject to a superradiant instability, growing a cloud of massive vector particles around it. In this work, we consider what happens if such a dark matter candidate field mimicking a dark photon interacts with an accretion flow onto the black hole. By including a kinetic mixing term with the standard model photon, we extend the commonly used equations of general-relativistic magnetohydrodynamics to a dark photon constituent. The coupling to the dark photon then appears as an effective dynamo term together with a dark Lorentz force acting on the accreting matter. We numerically study the interactions between the superradiant dark photon cloud and the inner accretion flow by solving the coupled system in full numerical relativity. By parameterically varying the mixing parameter between the dark and standard model sector, we provide a first investigation of how the accretion flow could be modified. Depending on the coupling strength, our solutions exhibit increased wind launching, as well as oscillation modes in the disk.
",
"doi": "10.1103/PhysRevD.111.063050",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2025-03-15",
"series_number": "6",
"volume": "111",
"issue": "6",
"pages": "063050"
},
{
"id": "authors:w0x45-20682",
"collection": "authors",
"collection_id": "w0x45-20682",
"cite_using_url": "https://authors.library.caltech.edu/records/w0x45-20682",
"type": "article",
"title": "Influence of muons, pions, and trapped neutrinos on neutron star mergers",
"author": [
{
"family_name": "Pajkos",
"given_name": "Michael A.",
"orcid": "0000-0002-4983-4589",
"clpid": "Pajkos-Michael-A"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "The merger of two neutron stars probes dense matter in a hot, neutrino-trapped regime. In this work, we investigate how fully accounting for pions (\ud835\udf0b), muons (\ud835\udf07), and muon-type neutrinos (\ud835\udf08\ud835\udf07) in the trapped regime may affect the outcome of the merger. By performing fully general-relativistic hydrodynamics simulations of merging neutron stars with equations of state to which we systematically add those different particle species, we aim to provide a detailed assessment of the impact of muons and pions on the merger and postmerger phases. In particular, we investigate the merger thermodynamics, mass ejection, and gravitational wave emission. Our findings are consistent with previous expectations, that the inclusion of such microphysical degrees of freedom and finite temperature corrections leads to frequency shifts on the order of 100–200 Hz in the postmerger gravitational wave signal, relative to a fiducial cold nucleonic equation-of-state model.
",
"doi": "10.1103/physrevd.111.043013",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2025-02-06",
"series_number": "4",
"volume": "111",
"issue": "4",
"pages": "043013"
},
{
"id": "authors:cgnax-m9s26",
"collection": "authors",
"collection_id": "cgnax-m9s26",
"cite_using_url": "https://authors.library.caltech.edu/records/cgnax-m9s26",
"type": "article",
"title": "Dual Jet Interaction, Magnetically Arrested Flows, and Flares in Accreting Binary Black Holes",
"author": [
{
"family_name": "Ressler",
"given_name": "Sean M.",
"orcid": "0000-0003-0220-5723"
},
{
"family_name": "Combi",
"given_name": "Luciano",
"orcid": "0000-0002-5427-1207"
},
{
"family_name": "Ripperda",
"given_name": "Bart",
"orcid": "0000-0002-7301-3908"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "\n
Supermassive binary black holes in galactic centers are potential multimessenger sources in gravitational waves and electromagnetic radiation. To find such objects, isolating unique electromagnetic signatures of their accretion flow is key. With the aid of three-dimensional general-relativistic magnetohydrodynamic simulations that utilize an approximate, semianalytic, superimposed spacetime metric, we identify two such signatures for merging binaries. Both involve magnetic reconnection and are analogous to plasma processes observed in the solar corona. The first, like colliding flux tubes that can cause solar flares, involves colliding jets that form an extended reconnection layer, dissipating magnetic energy and causing the two jets to merge. The second, akin to coronal mass ejection events, involves the accretion of magnetic field lines onto both black holes; these magnetic fields then twist, inflate, and form a trailing current sheet, ultimately reconnecting and driving a hot outflow. We provide estimates for the associated electromagnetic emission for both processes, showing that they likely accelerate electrons to high energies and are promising candidates for continuous, stochastic, and/or quasi-periodic higher-energy electromagnetic emission. We also show that the accretion flows around each black hole can display features associated with the magnetically arrested state. However, simulations with black hole spins misaligned with the orbital plane and simulations with larger Bondi radii saturate at lower values of horizon-penetrating magnetic flux than standard magnetically arrested disks, leading to weaker, intermittent jets owing to feedback from the weak jets or equatorial flux tubes ejected by reconnecting field lines near the horizon.
\n
A variety of high-energy astrophysical phenomena are powered by the release—via magnetic reconnection—of the energy stored in oppositely directed fields. Single-fluid resistive magnetohydrodynamic (MHD) simulations with uniform resistivity yield dissipation rates that are much lower (by nearly 1 order of magnitude) than equivalent kinetic calculations. Reconnection-driven phenomena could be accordingly modeled in resistive MHD employing a nonuniform, \"effective\" resistivity informed by kinetic calculations. In this work, we analyze a suite of fully kinetic particle-in-cell (PIC) simulations of relativistic pair-plasma reconnection—where the magnetic energy is greater than the rest mass energy—for different strengths of the guide field orthogonal to the alternating component. We extract an empirical prescription for the effective resistivity, η_(eff) = αB0 | J | p / ( | J | p+1 + (entc)p+1), where B0 is the reconnecting magnetic field strength, J is the current density, nt is the lab-frame total number density, e is the elementary charge, and c is the speed of light. The guide field dependence is encoded in α and p, which we fit to PIC data. This resistivity formulation—which relies only on single-fluid MHD quantities—successfully reproduces the spatial structure and strength of nonideal electric fields and thus provides a promising strategy for enhancing the reconnection rate in resistive MHD simulations.
",
"doi": "10.3847/2041-8213/ada158",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2025-01-10",
"series_number": "2",
"volume": "978",
"issue": "2",
"pages": "L45"
},
{
"id": "authors:cjeh6-hhx64",
"collection": "authors",
"collection_id": "cjeh6-hhx64",
"cite_using_url": "https://authors.library.caltech.edu/records/cjeh6-hhx64",
"type": "article",
"title": "Mass Transfer in Eccentric Black Hole\u2013Neutron Star Mergers",
"author": [
{
"family_name": "Zenati",
"given_name": "Yossef",
"orcid": "0000-0002-0632-8897"
},
{
"family_name": "Rozner",
"given_name": "Mor",
"orcid": "0000-0002-2728-0132"
},
{
"family_name": "Krolik",
"given_name": "Julian H.",
"orcid": "0000-0002-2995-7717"
},
{
"family_name": "Most",
"given_name": "Elias",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "\n
Black hole–neutron star binaries are of interest in many ways: they are intrinsically transient, radiate gravitational waves detectable by LIGO, and may produce γ-ray bursts. Although it has long been assumed that their late-stage orbital evolution is driven entirely by gravitational wave emission, we show here that in certain circumstances, mass transfer from the neutron star onto the black hole can both alter the binary's orbital evolution and significantly reduce the neutron star's mass: when the fraction of its mass transferred per orbit is \u227310−2, the neutron star's mass diminishes by order unity, leading to mergers in which the neutron star mass is exceptionally small. The mass transfer creates a gas disk around the black hole before merger that can be comparable in mass to the debris remaining after merger, i.e., ~0.1 M\u2299. These processes are most important when the initial neutron star–black hole mass ratio q is in the range ≈0.2–0.8, the orbital semimajor axis is 40 \u2272 a0/rg \u2272 300 (rg ≡ GMBH/c2), and the eccentricity is large at e0 \u2273 0.8. Systems of this sort may be generated through the dynamical evolution of a triple system, as well as by other means.
\n
We present a discontinuous Galerkin-finite difference hybrid scheme that allows high-order shock capturing with the discontinuous Galerkin method for general relativistic magnetohydrodynamics in dynamical spacetimes. We present several optimizations and stability improvements to our algorithm that allow the hybrid method to successfully simulate single, rotating, and binary neutron stars. The hybrid method achieves the efficiency of discontinuous Galerkin methods throughout almost the entire spacetime during the inspiral phase, while being able to robustly capture shocks and resolve the stellar surfaces. We also use Cauchy-characteristic evolution to compute the first gravitational waveforms at future null infinity from binary neutron star mergers. The simulations presented here are the first successful binary neutron star inspiral and merger simulations using discontinuous Galerkin methods.
",
"doi": "10.1088/1361-6382/ad88cf",
"issn": "0264-9381",
"publisher": "IOP Publishing",
"publication": "Classical and Quantum Gravity",
"publication_date": "2024-12-19",
"series_number": "24",
"volume": "41",
"issue": "24",
"pages": "245002"
},
{
"id": "authors:sezs5-32n63",
"collection": "authors",
"collection_id": "sezs5-32n63",
"cite_using_url": "https://authors.library.caltech.edu/records/sezs5-32n63",
"type": "article",
"title": "Theoretical and experimental constraints for the equation of state of dense and hot matter",
"author": [
{
"family_name": "Kumar",
"given_name": "Rajesh",
"orcid": "0000-0003-2746-3956",
"clpid": "Kumar-Rajesh"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626"
},
{
"family_name": "Jahan",
"given_name": "Johannes",
"orcid": "0000-0002-4557-4652"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272"
},
{
"family_name": "Noronha-Hostler",
"given_name": "Jacquelyn",
"orcid": "0000-0003-3229-4958"
},
{
"family_name": "Ratti",
"given_name": "Claudia",
"orcid": "0000-0002-8335-567X"
},
{
"family_name": "Yunes",
"given_name": "Nico",
"orcid": "0000-0001-6147-1736"
},
{
"family_name": "Nava Acuna",
"given_name": "Angel Rodrigo",
"orcid": "0000-0001-5562-3254"
},
{
"family_name": "Alford",
"given_name": "Mark",
"orcid": "0000-0001-9675-7005"
},
{
"family_name": "Anik",
"given_name": "Mahmudul Hasan",
"orcid": "0000-0003-0256-083X"
},
{
"family_name": "Chatterjee",
"given_name": "Debarati"
},
{
"family_name": "Chatziioannou",
"given_name": "Katerina",
"orcid": "0000-0002-5833-413X",
"clpid": "Chatziioannou-K"
},
{
"family_name": "Chen",
"given_name": "Hsin-Yu",
"orcid": "0000-0001-5403-3762"
},
{
"family_name": "Clevinger",
"given_name": "Alexander",
"orcid": "0000-0001-6478-7066"
},
{
"family_name": "Conde",
"given_name": "Carlos"
},
{
"family_name": "Cruz Camacho",
"given_name": "Nikolas"
},
{
"family_name": "Dore",
"given_name": "Travis",
"orcid": "0000-0001-5686-3954"
},
{
"family_name": "Drischler",
"given_name": "Christian",
"orcid": "0000-0003-1534-6285"
},
{
"family_name": "Elfner",
"given_name": "Hannah",
"orcid": "0000-0002-6213-3613"
},
{
"family_name": "Essick",
"given_name": "Reed",
"orcid": "0000-0001-8196-9267"
},
{
"family_name": "Friedenberg",
"given_name": "David"
},
{
"family_name": "Ghosh",
"given_name": "Suprovo",
"orcid": "0000-0002-1656-9870"
},
{
"family_name": "Grefa",
"given_name": "Joaquin",
"orcid": "0000-0001-7590-9364"
},
{
"family_name": "Haas",
"given_name": "Roland",
"orcid": "0000-0003-1424-6178"
},
{
"family_name": "Haber",
"given_name": "Alexander"
},
{
"family_name": "Hammelmann",
"given_name": "Jan"
},
{
"family_name": "Harris",
"given_name": "Steven",
"orcid": "0000-0002-0809-983X"
},
{
"family_name": "Haster",
"given_name": "Carl-Johan",
"orcid": "0000-0001-8040-9807"
},
{
"family_name": "Hatsuda",
"given_name": "Tetsuo",
"orcid": "0000-0003-2206-9810"
},
{
"family_name": "Hippert",
"given_name": "Mauricio",
"orcid": "0000-0001-5802-3908"
},
{
"family_name": "Hirayama",
"given_name": "Renan",
"orcid": "0000-0003-2403-8073"
},
{
"family_name": "Holt",
"given_name": "Jeremy W.",
"orcid": "0000-0003-4373-3856"
},
{
"family_name": "Kahangirwe",
"given_name": "Micheal"
},
{
"family_name": "Karthein",
"given_name": "Jamie",
"orcid": "0000-0003-2041-5206"
},
{
"family_name": "Kojo",
"given_name": "Toru",
"orcid": "0000-0001-5656-3652"
},
{
"family_name": "Landry",
"given_name": "Philippe",
"orcid": "0000-0002-8457-1964"
},
{
"family_name": "Lin",
"given_name": "Zidu",
"orcid": "0000-0003-3357-5460"
},
{
"family_name": "Luzum",
"given_name": "Matthew",
"orcid": "0000-0002-0367-7055"
},
{
"family_name": "Manning",
"given_name": "T. Andrew"
},
{
"family_name": "Salinas San Martin",
"given_name": "Jordi",
"orcid": "0000-0001-6203-4458"
},
{
"family_name": "Miller",
"given_name": "Cole",
"orcid": "0000-0002-2666-728X"
},
{
"family_name": "Most",
"given_name": "Elias Roland",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Mroczek",
"given_name": "Debora",
"orcid": "0000-0002-5417-6189"
},
{
"family_name": "Muronga",
"given_name": "Azwinndini",
"orcid": "0000-0003-3501-5272"
},
{
"family_name": "Patino",
"given_name": "Nicolas"
},
{
"family_name": "Peterson",
"given_name": "Jeffrey"
},
{
"family_name": "Plumberg",
"given_name": "Christopher",
"orcid": "0000-0001-6678-3966"
},
{
"family_name": "Price",
"given_name": "Damien"
},
{
"family_name": "Providencia",
"given_name": "Constanca",
"orcid": "0000-0001-6464-8023"
},
{
"family_name": "Rougemont",
"given_name": "Romulo",
"orcid": "0000-0002-1558-1624"
},
{
"family_name": "Roy",
"given_name": "Satyajit"
},
{
"family_name": "Shah",
"given_name": "Hitansh"
},
{
"family_name": "Shapiro",
"given_name": "Stuart",
"orcid": "0000-0002-3263-7386"
},
{
"family_name": "Steiner",
"given_name": "Andrew W.",
"orcid": "0000-0003-2478-4017"
},
{
"family_name": "Strickland",
"given_name": "Michael",
"orcid": "0000-0003-0489-4278"
},
{
"family_name": "Tan",
"given_name": "Hung",
"orcid": "0000-0001-9101-048X"
},
{
"family_name": "Togashi",
"given_name": "Hajime",
"orcid": "0000-0003-3199-8646"
},
{
"family_name": "Portillo Vazquez",
"given_name": "Israel",
"orcid": "0000-0001-7774-3521"
},
{
"family_name": "Wen",
"given_name": "Pengsheng",
"orcid": "0000-0003-4377-7058"
},
{
"family_name": "Zhang",
"given_name": "Ziyuan",
"orcid": "0000-0003-4795-0882"
},
{
"literal": "MUSES Collaboration"
}
],
"abstract": "\n
\n
This review aims at providing an extensive discussion of modern constraints relevant for dense and hot strongly interacting matter. It includes theoretical first-principle results from lattice and perturbative QCD, as well as chiral effective field theory results. From the experimental side, it includes heavy-ion collision and low-energy nuclear physics results, as well as observations from neutron stars and their mergers. The validity of different constraints, concerning specific conditions and ranges of applicability, is also provided.
\n
\n
We perform the first magnetohydrodynamic simulation tracking the magnetosphere of a collapsing magnetar. The collapse is expected for massive rotating magnetars formed in merger events and may occur many hours after the merger. Our simulation suggests a novel mechanism for a gamma-ray burst (GRB), which is uncollimated and forms a delayed high-energy counterpart of the merger gravitational waves. The simulation shows that the collapse launches an outgoing magnetospheric shock, and a hot magnetized outflow forms behind the shock. The outflow is baryon free and uncollimated, and its power peaks on a millisecond timescale. Then, the outflow becomes modulated by the ring-down of the nascent black hole, imprinting its kilohertz quasi-normal modes on the GRB tail.
",
"doi": "10.3847/2041-8213/ad7e1f",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2024-10-10",
"series_number": "1",
"volume": "974",
"issue": "1",
"pages": "L12"
},
{
"id": "authors:sd07f-h7677",
"collection": "authors",
"collection_id": "sd07f-h7677",
"cite_using_url": "https://authors.library.caltech.edu/records/sd07f-h7677",
"type": "article",
"title": "Nonlinear Alfv\u00e9n-wave Dynamics and Premerger Emission from Crustal Oscillations in Neutron Star Mergers",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Kim",
"given_name": "Yoonsoo",
"orcid": "0000-0002-4305-6026",
"clpid": "Kim-Yoonsoo"
},
{
"family_name": "Chatziioannou",
"given_name": "Katerina",
"orcid": "0000-0002-5833-413X",
"clpid": "Chatziioannou-K"
},
{
"family_name": "Legred",
"given_name": "Isaac",
"orcid": "0000-0002-9523-9617",
"clpid": "Legred-Isaac"
}
],
"abstract": "\n
Neutron stars have solid crusts threaded by strong magnetic fields. Perturbations in the crust can excite nonradial oscillations, which can in turn launch Alfvén waves into the magnetosphere. In the case of a compact binary close to merger involving at least one neutron star, this can happen through tidal interactions causing resonant excitations that shatter the neutron star crust. We present the first numerical study that elucidates the dynamics of Alfvén waves launched in a compact binary magnetosphere. We seed a magnetic field perturbation on the neutron star crust, which we then evolve in fully general-relativistic force-free electrodynamics using a GPU-based implementation. We show that Alfvén waves steepen nonlinearly before reaching the orbital light cylinder, form flares, and dissipate energy in a transient current sheet. Our results predict radio and X-ray precursor emission from this process.
\n
Binary systems with comparable masses and a surrounding accretion disk can accrete gas through spiral accretion streams penetrating the central cavity formed by tidal interactions. Using three-dimensional Newtonian magnetohydrodynamics simulations, we investigate the possibility of a magnetically arrested accretion flow through the cavity. Rather than solely continuously feeding the binary through spiral accretion streams, the accretion is regulated by the strong magnetic field inside the cavity. Transport of mass and angular momentum onto the binary then proceeds largely periodically in magnetic flux eruption episodes. The ejected flux tubes carry angular momentum outward and away from the binary, inject hot plasma into the disk, and can launch flares. This likely intermittent scenario could have potential implications for the emission signatures of supermassive black hole binaries and shed light onto the role magnetic fields play in the binary's orbital evolution.
",
"doi": "10.3847/2041-8213/ad7713",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2024-09-20",
"series_number": "1",
"volume": "973",
"issue": "1",
"pages": "L19"
},
{
"id": "authors:wg6r6-0qh17",
"collection": "authors",
"collection_id": "wg6r6-0qh17",
"cite_using_url": "https://authors.library.caltech.edu/records/wg6r6-0qh17",
"type": "article",
"title": "Neutron Star Atmosphere\u2013Ocean Dynamics",
"author": [
{
"family_name": "N\u00e4ttil\u00e4",
"given_name": "Joonas",
"orcid": "0000-0002-3226-4575"
},
{
"family_name": "Cho",
"given_name": "James Y-K.",
"orcid": "0000-0002-4525-5651"
},
{
"family_name": "Skinner",
"given_name": "Jack W.",
"orcid": "0000-0002-5263-385X"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Ripperda",
"given_name": "Bart",
"orcid": "0000-0002-7301-3908"
}
],
"abstract": "We analyze the structure and dynamics of the plasma atmospheres and Coulomb-liquid oceans on neutron stars. Salient dynamical parameters are identified and their values estimated for the governing set of magnetohydrodynamics equations. Neutron star atmospheres and oceans are strongly stratified and, depending on the rotation period, contain a multitude of long-lived vortices (spots) and/or narrow zonal jets (free-shear zones) in the large plasma-beta regime—i.e., βp \u226b 1 (hydrodynamic regime). In contrast, when βp \u2272 1 (magnetohydrodynamic regime), the flow is dominated by a global lattice of effectively fixed magnetic islands (plasmoids) without any jets. Understanding the spatiotemporal variability of dynamic atmospheres and oceans on neutron stars is crucial for interpreting observations of their X-ray emissions.
",
"doi": "10.3847/1538-4357/ad54c2",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2024-08-10",
"series_number": "1",
"volume": "971",
"issue": "1",
"pages": "37"
},
{
"id": "authors:7bjnb-kck30",
"collection": "authors",
"collection_id": "7bjnb-kck30",
"cite_using_url": "https://authors.library.caltech.edu/records/7bjnb-kck30",
"type": "article",
"title": "General relativistic force-free electrodynamics with a discontinuous Galerkin-finite difference hybrid method",
"author": [
{
"family_name": "Kim",
"given_name": "Yoonsoo",
"orcid": "0000-0002-4305-6026",
"clpid": "Kim-Yoonsoo"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Throwe",
"given_name": "William",
"orcid": "0000-0001-5059-4378",
"clpid": "Throwe-William"
},
{
"family_name": "Teukolsky",
"given_name": "Saul A.",
"orcid": "0000-0001-9765-4526",
"clpid": "Teukolsky-S-A"
},
{
"family_name": "Deppe",
"given_name": "Nils",
"orcid": "0000-0003-4557-4115",
"clpid": "Deppe-Nils"
}
],
"abstract": "Relativistic plasmas around compact objects can sometimes be approximated as being force-free. In this limit, the plasma inertia is negligible and the overall dynamics is governed by global electric currents. We present a novel numerical approach for simulating such force-free plasmas, which allows for high accuracy in smooth regions as well as capturing dissipation in current sheets. Using a high-order accurate discontinuous Galerkin method augmented with a conservative finite-difference method, we demonstrate efficient global simulations of black hole and neutron star magnetospheres. In addition to a series of challenging test problems, we show that our approach can—depending on the physical properties of the system and the numerical implementation—be up to 10× more efficient than conventional simulations, with a speedup of 2–3× for most problems we consider in practice.
",
"doi": "10.1103/physrevd.109.123019",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2024-06-15",
"series_number": "12",
"volume": "109",
"issue": "12",
"pages": "123019"
},
{
"id": "authors:71hq2-1xx97",
"collection": "authors",
"collection_id": "71hq2-1xx97",
"cite_using_url": "https://authors.library.caltech.edu/records/71hq2-1xx97",
"type": "article",
"title": "Emergence of Microphysical Bulk Viscosity in Binary Neutron Star Postmerger Dynamics",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Haber",
"given_name": "Alexander",
"orcid": "0000-0002-5511-9565",
"clpid": "Haber-Alexander"
},
{
"family_name": "Harris",
"given_name": "Steven P.",
"orcid": "0000-0002-0809-983X",
"clpid": "Harris-Steven-P"
},
{
"family_name": "Zhang",
"given_name": "Ziyuan",
"orcid": "0000-0003-4795-0882",
"clpid": "Zhang-Ziyuan"
},
{
"family_name": "Alford",
"given_name": "Mark G.",
"orcid": "0000-0001-9675-7005",
"clpid": "Alford-Mark-G"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272",
"clpid": "Noronha-Jorge"
}
],
"abstract": "\n
In nuclear matter in isolated neutron stars, the flavor content (e.g., proton fraction) is subject to weak interactions, establishing flavor (β-)equilibrium. However, there can be deviations from this equilibrium during the merger of two neutron stars. We study the resulting out-of-equilibrium dynamics during the collision by incorporating direct and modified Urca processes (in the neutrino-transparent regime) into general-relativistic hydrodynamics simulations with a simplified neutrino transport scheme. We demonstrate how weak-interaction-driven bulk viscosity in postmerger simulations can emerge and assess the bulk viscous dynamics of the resulting flow. We further place limits on the impact of the postmerger gravitational-wave strain. Our results show that weak-interaction-driven bulk viscosity can potentially lead to a phase shift of the postmerger gravitational-wave spectrum, although the effect is currently on the same level as the numerical errors of our simulation.
\n
In this work we provide a new, well-controlled expansion of the equation of state of dense matter from zero to finite temperatures (T), while covering a wide range of charge fractions (YQ), from pure neutron to isospin symmetric nuclear matter. Our expansion can be used to describe neutron star mergers and core-collapse supernova explosions using as a starting point neutron star observations, while maintaining agreement with laboratory data, in a model independent way. We suggest new thermodynamic quantities of interest that can be calculated from theoretical models or directly inferred by experimental data that can help constrain the finite T equation of state. With our new method, we can quantify the uncertainty in our finite T and YQ expansions in a well-controlled manner without making assumptions about the underlying degrees of freedom. We can reproduce results from a microscopic equation of state up to T=100 MeV for baryon chemical potential μB\u22731100 MeV (∼1−2 nsat) within 5% error, with even better results for larger μB and/or lower T. We investigate the sources of numerical and theoretical uncertainty and discuss future directions of study.
",
"doi": "10.48550/arxiv.2404.01658",
"publisher": "arXiv",
"publication_date": "2024-04-03"
},
{
"id": "authors:8pb6m-ef267",
"collection": "authors",
"collection_id": "8pb6m-ef267",
"cite_using_url": "https://authors.library.caltech.edu/records/8pb6m-ef267",
"type": "article",
"title": "Impact of a mean field dynamo on neutron star mergers leading to magnetar remnants",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
}
],
"abstract": "We investigate the impact of a mean field model for the \u03b1\u03a9 dynamo potentially active in the postmerger phase of a binary neutron star coalescence. We do so by deriving equations for ideal general relativistic magnetohydrodynamics with an additional \u03b1 term, which closely resemble their Newtonian counterpart, but remain compatible with standard numerical relativity simulations. We propose a heuristic dynamo closure relation for the magnetorotational instability-driven turbulent dynamo in the outer layers of a differentially rotating magnetar remnant and its accretion disk. As a first demonstration, we apply this framework to the early stages of post-merger evolution (\u227250\u2009\u2009ms). We demonstrate that depending on the efficacy of the dynamo action, magnetically driven outflows can be present with their amount of baryon loading correlating with the magnetic field amplification. These outflows can also contain precursor flaring episodes before settling into a quasisteady state. For the dynamo parameters explored in this work, we observe electromagnetic energy fluxes of up to 10\u2075\u2070\u2009\u2009erg/s, although larger amplification parameters will likely lead to stronger fluxes. Our results are consistent with the expectation that substantial dynamo amplification (either during or after the merger) may be necessary for neutron-star remnants to power short gamma-ray bursts or precursors thereof.
",
"doi": "10.1103/physrevd.108.123012",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2023-12-15",
"series_number": "12",
"volume": "108",
"issue": "12",
"pages": "123012"
},
{
"id": "authors:100t6-c8573",
"collection": "authors",
"collection_id": "100t6-c8573",
"cite_using_url": "https://authors.library.caltech.edu/records/100t6-c8573",
"type": "article",
"title": "Electromagnetic Precursors to Black Hole\u2013Neutron Star Gravitational Wave Events: Flares and Reconnection-powered Fast Radio Transients from the Late Inspiral",
"author": [
{
"family_name": "Most",
"given_name": "Elias",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Philippov",
"given_name": "Alexander A.",
"orcid": "0000-0001-7801-0362"
}
],
"abstract": "The presence of magnetic fields in the late inspiral of black hole–neutron star binaries could lead to potentially detectable electromagnetic precursor transients. Using general-relativistic force-free electrodynamics simulations, we investigate premerger interactions of the common magnetosphere of black hole–neutron star systems. We demonstrate that these systems can feature copious electromagnetic flaring activity, which we find depends on the magnetic field orientation but not on black hole spin. Due to interactions with the surrounding magnetosphere, these flares could lead to fast-radio-burst-like transients and X-ray emission, with LEM\u22721041(B∗/1012G)2ergs−1 as an upper bound on the luminosity, where B* is the magnetic field strength on the surface of the neutron star.
",
"doi": "10.3847/2041-8213/acfdae",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-10-20",
"series_number": "2",
"volume": "956",
"issue": "2",
"pages": "L33"
},
{
"id": "authors:1xcn4-v1f27",
"collection": "authors",
"collection_id": "1xcn4-v1f27",
"cite_using_url": "https://authors.library.caltech.edu/records/1xcn4-v1f27",
"type": "article",
"title": "Reconnection-Powered Fast Radio Transients from Coalescing Neutron Star Binaries",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Philippov",
"given_name": "Alexander A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
}
],
"abstract": "It is an open question whether and how gravitational wave events involving neutron stars can be preceded by electromagnetic counterparts. This Letter shows that the collision of two neutron stars with magnetic fields well below magnetar-level strengths can produce millisecond fast-radio-burst-like transients. Using global force-free electrodynamics simulations, we identify the coherent emission mechanism that might operate in the common magnetosphere of a binary neutron star system prior to merger. We predict that the emission show have frequencies in the range of 10–20 GHz for magnetic fields of \ud835\udc35*=10¹¹ G at the surfaces of the stars.
",
"doi": "10.1103/PhysRevLett.130.245201",
"issn": "0031-9007",
"publisher": "American Physical Society",
"publication": "Physical Review Letters",
"publication_date": "2023-06-16",
"volume": "130",
"pages": "245201"
},
{
"id": "authors:v39h4-xp636",
"collection": "authors",
"collection_id": "v39h4-xp636",
"cite_using_url": "https://authors.library.caltech.edu/records/v39h4-xp636",
"type": "article",
"title": "How do axisymmetric black holes grow monopole and dipole hair?",
"author": [
{
"family_name": "Hegade K. R.",
"given_name": "Abhishek",
"orcid": "0000-0002-4099-4359",
"clpid": "Hegade-K-R-Abihishek"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272",
"clpid": "Noronha-Jorge"
},
{
"family_name": "Witek",
"given_name": "Helvi",
"orcid": "0000-0003-3043-163X",
"clpid": "Witek-Helvi"
},
{
"family_name": "Yunes",
"given_name": "Nicol\u00e1s",
"orcid": "0000-0001-6147-1736",
"clpid": "Yunes-Nicol\u00e1s"
}
],
"abstract": "We study the dynamical formation of scalar monopole and dipole hair in scalar Gauss-Bonnet theory and dynamical Chern-Simons theory. We prove that the spherically symmetric mode of the dipole hair is completely determined by the product of the mass of the spacetime and the value of the monopole hair. We then show that the dynamics of the \u2113 =1 mode of the dipole hair is intimately tied to the appearance of the event horizon during axisymmetric collapse, which results in the radiation of certain modes that could have been divergent in the future of the collapse. We confirm these analytical predictions by simulating the gravitational collapse of a rapidly rotating neutron star in the decoupling limit, both in scalar Gauss-Bonnet and dynamical Chern-Simons theory. Our results, combined with those in Hegade K. R. et al. [Phys. Rev. D 105, 064041 (2022)], provide a clear physical picture of the dynamics of scalar monopole and dipole radiation in axisymmetric and spherical gravitational collapse in these theories.
",
"doi": "10.1103/PhysRevD.107.104047",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2023-05-19",
"volume": "107",
"pages": "104047"
},
{
"id": "authors:31zvg-hve27",
"collection": "authors",
"collection_id": "31zvg-hve27",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-887064000.1",
"type": "article",
"title": "Three-dimensional Dynamics of Strongly Twisted Magnetar Magnetospheres: Kinking Flux Tubes and Global Eruptions",
"author": [
{
"family_name": "Mahlmann",
"given_name": "J. F.",
"orcid": "0000-0002-5349-7116",
"clpid": "Mahlmann-Jens-Florian"
},
{
"family_name": "Philippov",
"given_name": "A. A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
},
{
"family_name": "Mewes",
"given_name": "V.",
"orcid": "0000-0001-5869-8542",
"clpid": "Mewes-Vassilios"
},
{
"family_name": "Ripperda",
"given_name": "B.",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Bart"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Sironi",
"given_name": "L.",
"orcid": "0000-0002-1227-2754",
"clpid": "Sironi-Lorenzo"
}
],
"abstract": "The origins of the various outbursts of hard X-rays from magnetars (highly magnetized neutron stars) are still unknown. We identify instabilities in relativistic magnetospheres that can explain a range of X-ray flare luminosities. Crustal surface motions can twist the magnetar magnetosphere by shifting the frozen-in footpoints of magnetic field lines in current-carrying flux bundles. Axisymmetric (2D) magnetospheres exhibit strong eruptive dynamics, i.e., catastrophic lateral instabilities triggered by a critical footpoint displacement of \u03c8_(crit) \u2273 \u03c0. In contrast, our new three-dimensional (3D) twist models with finite surface extension capture important non-axisymmetric dynamics of twisted force-free flux bundles in dipolar magnetospheres. Besides the well-established global eruption resulting (as in 2D) from lateral instabilities, such 3D structures can develop helical, kink-like dynamics, and dissipate energy locally (confined eruptions). Up to 25% of the induced twist energy is dissipated and available to power X-ray flares in powerful global eruptions, with most of our models showing an energy release in the range of the most common X-ray outbursts, \u227210\u2074\u00b3 erg. Such events occur when significant energy builds up while deeply buried in the dipole magnetosphere. Less energetic outbursts likely precede powerful flares, due to intermittent instabilities and confined eruptions of a continuously twisting flux tube. Upon reaching a critical state, global eruptions produce the necessary Poynting-flux-dominated outflows required by models prescribing the fast radio burst production in the magnetar wind\u2014for example, via relativistic magnetic reconnection or shocks.",
"doi": "10.3847/2041-8213/accada",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-04-20",
"series_number": "2",
"volume": "947",
"issue": "2",
"pages": "Art. No. L34"
},
{
"id": "authors:naytm-n1z09",
"collection": "authors",
"collection_id": "naytm-n1z09",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-604958000.2",
"type": "article",
"title": "Flares, Jets, and Quasiperiodic Outbursts from Neutron Star Merger Remnants",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
}
],
"abstract": "Using numerical relativity simulations with a subgrid dynamo prescription to generate strong initial magnetic fields, we investigate the possibility of launching a jet-like outflow from the hypermassive neutron star (HMNS) during the early stages of the merger, prior to the remnant's collapse to a black hole. We demonstrate that buoyant instabilities in the strongly magnetized HMNS can lead to a periodic emission of powerful electromagnetic flares shortly after the merger. These are followed by a collimated mildly relativistic outflow. Both types of outflows feature quasiperiodic kilohertz substructure. These early-time outflows may power precursors to short-duration gamma-ray bursts (sGRBs) or in some cases the entire sGRB. While the overall temporal power spectrum we find broadly agrees with the one recently reported for quasiperiodic oscillations in the sGRB GRB910711, our simulations suggest that the periodic electromagnetic substructure is dominated by magnetohydrodynamic shearing processes rather than correlating with the corresponding postmerger gravitational-wave signal.",
"doi": "10.3847/2041-8213/acca84",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-04-10",
"series_number": "1",
"volume": "947",
"issue": "1",
"pages": "Art. No. L15"
},
{
"id": "authors:qx4z4-byn24",
"collection": "authors",
"collection_id": "qx4z4-byn24",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-296239000.1",
"type": "monograph",
"title": "Flares, jets and quasi-periodic outbursts from neutron star merger remnants",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Quataert",
"given_name": "Eliot",
"orcid": "0000-0001-9185-5044",
"clpid": "Quataert-Eliot"
}
],
"abstract": "Using numerical relativity simulations with a subgrid dynamo prescription to generate strong initial magnetic fields, we investigate the possibility of launching a jet-like outflow from the hypermassive neutron star (HMNS) during the early stages of the merger, prior to the remnants collapse to a black hole. We demonstrate that buoyant instabilities in the strongly magnetized HMNS can lead to a periodic emission of powerful electromagnetic flares shortly after the merger. These are followed by a collimated mildly relativistic outflow. Both types of outflows feature quasi-periodic kilohertz substructure. These early-time outflows may power precursors to short-duration gamma-ray bursts (SGRB) or in some cases the entire SGRB. While the overall temporal power spectrum we find broadly agrees with the one recently reported for quasi-periodic oscillations in the SGRB GRB910711, our simulations suggest that the periodic electromagnetic substructure is dominated by magnetohydrodynamic shearing processes rather than correlating with the corresponding post-merger gravitational wave signal.",
"publisher": "arXiv",
"publication_date": "2023-03-14"
},
{
"id": "authors:6srf3-1j041",
"collection": "authors",
"collection_id": "6srf3-1j041",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-296716000.5",
"type": "article",
"title": "Crustal Magnetic Fields Do Not Lead to Large Magnetic-field Amplifications in Binary Neutron Star Mergers",
"author": [
{
"family_name": "Chabanov",
"given_name": "Michail",
"orcid": "0000-0001-9676-765X",
"clpid": "Chabanov-Michail"
},
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The amplification of magnetic fields plays an important role in explaining numerous astrophysical phenomena associated with binary neutron star mergers, such as mass ejection and the powering of short gamma-ray bursts. Magnetic fields in isolated neutron stars are often assumed to be confined to a small region near the stellar surface, while they are normally taken to fill the whole star in numerical modeling of mergers. By performing high-resolution, global, and high-order general-relativistic magnetohydrodynamic simulations, we investigate the impact of a purely crustal magnetic field and contrast it with the standard configuration consisting of a dipolar magnetic field with the same magnetic energy but filling the whole star. While the crust configurations are very effective in generating strong magnetic fields during the Kelvin\u2013Helmholtz-instability stage, they fail to achieve the same level of magnetic-field amplification of the full-star configurations. This is due to the lack of magnetized material in the neutron-star interiors to be used for further turbulent amplification and to the surface losses of highly magnetized matter in the crust configurations. Hence, the final magnetic energies in the two configurations differ by more than 1 order of magnitude. We briefly discuss the impact of these results on astrophysical observables and how they can be employed to deduce the magnetic topology in merging binaries.",
"doi": "10.3847/2041-8213/acbbc5",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-03-01",
"series_number": "1",
"volume": "945",
"issue": "1",
"pages": "Art. No. L14"
},
{
"id": "authors:gne0g-j3e32",
"collection": "authors",
"collection_id": "gne0g-j3e32",
"cite_using_url": "https://authors.library.caltech.edu/records/gne0g-j3e32",
"type": "article",
"title": "Crustal Magnetic Fields Do Not Lead to Large Magnetic-field Amplifications in Binary Neutron Star Mergers",
"author": [
{
"family_name": "Chabanov",
"given_name": "Michail",
"orcid": "0000-0001-9676-765X",
"clpid": "Chabanov-Michail"
},
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "\n
The amplification of magnetic fields plays an important role in explaining numerous astrophysical phenomena associated with binary neutron star mergers, such as mass ejection and the powering of short gamma-ray bursts. Magnetic fields in isolated neutron stars are often assumed to be confined to a small region near the stellar surface, while they are normally taken to fill the whole star in numerical modeling of mergers. By performing high-resolution, global, and high-order general-relativistic magnetohydrodynamic simulations, we investigate the impact of a purely crustal magnetic field and contrast it with the standard configuration consisting of a dipolar magnetic field with the same magnetic energy but filling the whole star. While the crust configurations are very effective in generating strong magnetic fields during the Kelvin–Helmholtz-instability stage, they fail to achieve the same level of magnetic-field amplification of the full-star configurations. This is due to the lack of magnetized material in the neutron-star interiors to be used for further turbulent amplification and to the surface losses of highly magnetized matter in the crust configurations. Hence, the final magnetic energies in the two configurations differ by more than 1 order of magnitude. We briefly discuss the impact of these results on astrophysical observables and how they can be employed to deduce the magnetic topology in merging binaries.
\n
The Einstein and Maxwell equations are both systems of hyperbolic equations which need to satisfy a set of elliptic constraints throughout evolution. However, while electrodynamics and magnetohydrodynamics have benefited from a large number of evolution schemes that are able to enforce these constraints and are easily applicable to curvilinear coordinates, unstructured meshes, or \ud835\udc41-body simulations, many of these techniques cannot be straightforwardly applied to existing formulations of the Einstein equations. We develop a 3+1 a formulation of the Einstein equations that shows a striking resemblance to the equations of relativistic magnetohydrodynamics and to electrodynamics in material media. The fundamental variables of this formulation are the frame fields, their exterior derivatives, and the Nester-Witten and Sparling forms. These mirror the roles of the electromagnetic four potential, the electromagnetic field strengths, the field excitations and the electric current. The role of the lapse function and shift vector, corresponds exactly to that of the scalar electric potential. The formulation is manifestly first order and flux-conservative, which makes it suitable for high-resolution shock capturing schemes and finite-element methods. Being derived as a system of equations in exterior derivatives, it is directly applicable to any coordinate system and to unstructured meshes, and leads to a natural discretization potentially suitable for the use of machine-precision constraint propagation techniques such as the Yee algorithm and constrained transport. Due to these properties, we expect this new formulation to be beneficial in simulations of many astrophysical systems, such as binary compact objects and core-collapse supernovae as well as cosmological simulations of the early Universe.
",
"doi": "10.1103/PhysRevD.105.124038",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2022-06-17",
"volume": "105",
"pages": "124038"
},
{
"id": "authors:nfggk-e6k52",
"collection": "authors",
"collection_id": "nfggk-e6k52",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297013000.21",
"type": "article",
"title": "Conservative finite volume scheme for first-order viscous relativistic hydrodynamics",
"author": [
{
"family_name": "Pandya",
"given_name": "Alex",
"orcid": "0000-0001-5197-2393",
"clpid": "Pandya-Alex"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Pretorius",
"given_name": "Frans",
"orcid": "0000-0001-8399-2217",
"clpid": "Pretorius-Frans"
}
],
"abstract": "We present the first conservative finite volume numerical scheme for the causal, stable relativistic Navier-Stokes equations developed by Bemfica, Disconzi, Noronha, and Kovtun (BDNK). BDNK theory has arisen very recently as a promising means of incorporating entropy-generating effects (viscosity, heat conduction) into relativistic fluid models, appearing as a possible alternative to the so-called M\u00fcller-Israel-Stewart (MIS) theory successfully used to model quark-gluon plasma. The major difference between the two lies in the structure of the system of partial differential equations (PDEs): BDNK theory only has a set of conservation laws, whereas MIS also includes a set of evolution equations for its dissipative degrees of freedom. The simpler structure of the BDNK PDEs in this respect allows for rigorous proofs of stability, causality, and hyperbolicity in full generality which have as yet been impossible for MIS. To capitalize on these advantages, we present the first fully conservative multidimensional fluid solver for the BDNK equations suitable for physical applications. The scheme includes a flux-conservative discretization, nonoscillatory reconstruction, and a central-upwind numerical flux and is designed to smoothly transition to a high-resolution shock-capturing perfect fluid solver in the inviscid limit. We assess the robustness of our new method in a series of flat-spacetime tests for a conformal fluid and provide a detailed comparison with previous approaches of Pandya and Pretorius [Phys. Rev. D 104, 023015 (2021)].",
"doi": "10.1103/physrevd.105.123001",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2022-06-15",
"series_number": "12",
"volume": "105",
"issue": "12",
"pages": "Art. No. 123001"
},
{
"id": "authors:d1sn5-d4x27",
"collection": "authors",
"collection_id": "d1sn5-d4x27",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297101000.29",
"type": "article",
"title": "New first-order formulation of the Einstein equations exploiting analogies with electrodynamics",
"author": [
{
"family_name": "Olivares",
"given_name": "H.",
"orcid": "0000-0001-6833-7580",
"clpid": "Olivares-S\u00e1nchez-H\u00e9ctor-Ra\u00fal"
},
{
"family_name": "Peshkov",
"given_name": "I.\u2009M.",
"orcid": "0000-0001-8285-0639",
"clpid": "Peshkov-Ilya-M"
},
{
"family_name": "Most",
"given_name": "E.\u2009R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Guercilena",
"given_name": "F.\u2009M.",
"orcid": "0000-0003-3824-4433",
"clpid": "Guercilena-Federico-M"
},
{
"family_name": "Papenfort",
"given_name": "L.\u2009J.",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
}
],
"abstract": "The Einstein and Maxwell equations are both systems of hyperbolic equations which need to satisfy a set of elliptic constraints throughout evolution. However, while electrodynamics and magnetohydrodynamics have benefited from a large number of evolution schemes that are able to enforce these constraints and are easily applicable to curvilinear coordinates, unstructured meshes, or N-body simulations, many of these techniques cannot be straightforwardly applied to existing formulations of the Einstein equations. We develop a 3 + 1 a formulation of the Einstein equations that shows a striking resemblance to the equations of relativistic magnetohydrodynamics and to electrodynamics in material media. The fundamental variables of this formulation are the frame fields, their exterior derivatives, and the Nester-Witten and Sparling forms. These mirror the roles of the electromagnetic four potential, the electromagnetic field strengths, the field excitations and the electric current. The role of the lapse function and shift vector, corresponds exactly to that of the scalar electric potential. The formulation is manifestly first order and flux-conservative, which makes it suitable for high-resolution shock capturing schemes and finite-element methods. Being derived as a system of equations in exterior derivatives, it is directly applicable to any coordinate system and to unstructured meshes, and leads to a natural discretization potentially suitable for the use of machine-precision constraint propagation techniques such as the Yee algorithm and constrained transport. Due to these properties, we expect this new formulation to be beneficial in simulations of many astrophysical systems, such as binary compact objects and core-collapse supernovae as well as cosmological simulations of the early Universe.",
"doi": "10.1103/physrevd.105.124038",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2022-06-15",
"series_number": "12",
"volume": "105",
"issue": "12",
"pages": "Art. No. 124038"
},
{
"id": "authors:w0vpg-6fs38",
"collection": "authors",
"collection_id": "w0vpg-6fs38",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-77156000.2",
"type": "monograph",
"title": "Magnetar bursts due to Alfv\u00e9n wave nonlinear breakout",
"author": [
{
"family_name": "Yuan",
"given_name": "Yajie",
"orcid": "0000-0002-0108-4774",
"clpid": "Yuan-Yajie"
},
{
"family_name": "Beloborodov",
"given_name": "Andrei M.",
"orcid": "0000-0001-5660-3175",
"clpid": "Beloborodov-Andrei-M"
},
{
"family_name": "Chen",
"given_name": "Alexander Y.",
"orcid": "0000-0002-4738-1168",
"clpid": "Chen-Alexander-Y"
},
{
"family_name": "Levin",
"given_name": "Yuri",
"clpid": "Levin-Yuri"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Philippov",
"given_name": "Alexander A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
}
],
"abstract": "The most common form of magnetar activity is short X-ray bursts, with durations from milliseconds to seconds, and luminosities ranging from 10\u00b3\u2074\u201310\u2074\u00b3 erg s\u207b\u00b9. Recently, an X-ray burst from the galactic magnetar SGR 1935+2154 was detected to be coincident with two fast radio burst (FRB) like events from the same source, providing evidence that FRBs may be linked to magnetar bursts. Using fully 3D force-free electrodynamics simulations, we show that such magnetar bursts may be produced by Alfv\u00e9n waves launched from localized magnetar quakes: a wave packet propagates to the outer magnetosphere, becomes nonlinear, and escapes the magnetosphere, forming an ultra-relativistic ejecta. The ejecta pushes open the magnetospheric field lines, creating current sheets behind it. Magnetic reconnection can happen at these current sheets, leading to plasma energization and X-ray emission. The angular size of the ejecta can be compact, \u22721 sr if the quake launching region is small, \u22720.01 sr at the stellar surface. We discuss implications for the FRBs and the coincident X-ray burst from SGR 1935+2154.",
"publisher": "arXiv",
"publication_date": "2022-04-18"
},
{
"id": "authors:ef9qy-0ps88",
"collection": "authors",
"collection_id": "ef9qy-0ps88",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-992796000.1",
"type": "article",
"title": "Weak Alfv\u00e9nic turbulence in relativistic plasmas. Part 2. Current sheets and dissipation \u2013 ERRATUM",
"author": [
{
"family_name": "Ripperda",
"given_name": "B.",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Barrt"
},
{
"family_name": "Mahlmann",
"given_name": "J. F.",
"orcid": "0000-0002-5349-7116",
"clpid": "Mahlmann-Jens-Florian"
},
{
"family_name": "Chernoglazov",
"given_name": "A.",
"orcid": "0000-0001-5121-1594",
"clpid": "Chernoglazov-Alexander"
},
{
"family_name": "TenBarge",
"given_name": "J. M.",
"orcid": "0000-0003-0143-951X",
"clpid": "TenBarge-Jason-M"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Juno",
"given_name": "J.",
"orcid": "0000-0001-6835-273X",
"clpid": "Juno-James"
},
{
"family_name": "Philippov",
"given_name": "A. A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
},
{
"family_name": "Bhattacharjee",
"given_name": "A.",
"clpid": "Bhattacharjee-A"
}
],
"abstract": "The original version of this paper was published with an incorrectly formatted title. The correct title is 'Weak Alfv\u00e9nic turbulence in relativistic plasmas. Part 2. Current sheets and dissipation'. This is important because it should be consistent with its accompanying paper 'Weak Alfv\u00e9nic turbulence in relativistic plasmas. Part 1. Dynamical equations and basic dynamics of interacting resonant triads'. The original version has now been updated.",
"doi": "10.1017/s0022377822000198",
"issn": "0022-3778",
"publisher": "Cambridge University Press",
"publication": "Journal of Plasma Physics",
"publication_date": "2022-04",
"series_number": "2",
"volume": "88",
"issue": "2",
"pages": "Art. No. 945880201"
},
{
"id": "authors:8xb7d-x9525",
"collection": "authors",
"collection_id": "8xb7d-x9525",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297037000.23",
"type": "article",
"title": "How do spherical black holes grow monopole hair?",
"author": [
{
"family_name": "Hegade K.\u2009R.",
"given_name": "Abhishek",
"orcid": "0000-0002-4099-4359",
"clpid": "Hegade-K-R-Abishek"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272",
"clpid": "Noronha-Jorge"
},
{
"family_name": "Witek",
"given_name": "Helvi",
"orcid": "0000-0003-3043-163X",
"clpid": "Witek-Helvi"
},
{
"family_name": "Yunes",
"given_name": "Nicol\u00e1s",
"orcid": "0000-0001-6147-1736",
"clpid": "Yunes-Nicol\u00e1s"
}
],
"abstract": "Black holes in certain modified gravity theories that contain a scalar field coupled to curvature invariants are known to possess (monopole) scalar hair while non-black-hole spacetimes (like neutron stars) do not. Therefore, as a neutron star collapses to a black hole, scalar hair must grow until it settles to the stationary black hole solution with (monopole) hair. In this paper, we study this process in detail and show that the growth of scalar hair is tied to the appearance and growth of the event horizon (before an apparent horizon forms), which forces scalar modes that would otherwise (in the future) become divergent to be radiated away. We prove this result rigorously in general first for a large class of modified theories, and then we exemplify the results by studying the temporal evolution of the scalar field in scalar Gauss-Bonnet gravity in two backgrounds: (i) a collapsing Oppenheimer-Snyder background, and (ii) a collapsing neutron star background. In case (i), we find an exact scalar field solution analytically, while in case (ii) we solve for the temporal evolution of the scalar field numerically, with both cases supporting the conclusion presented above. Our results suggest that the emission of a burst of scalar field radiation is a necessary condition for black hole formation in a large class of modified theories of gravity.",
"doi": "10.1103/physrevd.105.064041",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2022-03-15",
"series_number": "6",
"volume": "105",
"issue": "6",
"pages": "Art. No. 064041"
},
{
"id": "authors:99rx2-rcx24",
"collection": "authors",
"collection_id": "99rx2-rcx24",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297052000.25",
"type": "monograph",
"title": "Probing neutron-star matter in the lab: similarities and differences between binary mergers and heavy-ion collisions",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Motornenko",
"given_name": "Anton",
"orcid": "0000-0003-3037-9923",
"clpid": "Motornenko-Anton"
},
{
"family_name": "Steinheimer",
"given_name": "Jan",
"orcid": "0000-0003-2565-7503",
"clpid": "Steinheimer-Jan"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
},
{
"family_name": "Stoecker",
"given_name": "Horst",
"orcid": "0000-0002-3282-3664",
"clpid": "Stoecker-Horst"
}
],
"abstract": "Binary neutron-star mergers and heavy-ion collisions are related through the properties of the hot and dense nuclear matter formed during these extreme events. In particular, low-energy heavy-ion collisions offer exciting prospects to recreate such extreme conditions in the laboratory. However, it remains unexplored to what degree those collisions can actually reproduce hot and dense matter formed in binary neutron star mergers. As a way to understand similarities and differences between these systems, we discuss their geometry and perform a direct numerical comparison of the thermodynamic conditions probed in both collisions. To enable a direct comparison, we employ a finite-temperature equation of state able to describe the entire high-energy phase diagram of quantum chromodynamics. Putting side by side the evolution of both systems, we find that laboratory heavy-ion collisions at the energy range of E_(lab) = 0.4\u20130.6 A MeV probe (thermodynamic) states of matter that are very similar to those created in binary neutron-star mergers. These results can inform future low-energy heavy-ion collisions probing this regime.",
"publisher": "arXiv",
"publication_date": "2022-01-31"
},
{
"id": "authors:7rtqt-ypa51",
"collection": "authors",
"collection_id": "7rtqt-ypa51",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297090000.28",
"type": "article",
"title": "Projecting the likely importance of weak-interaction-driven bulk viscosity in neutron star mergers",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Harris",
"given_name": "Steven P.",
"orcid": "0000-0002-0809-983X",
"clpid": "Harris-Steven-P"
},
{
"family_name": "Plumberg",
"given_name": "Christopher",
"orcid": "0000-0001-6678-3966",
"clpid": "Plumberg-Christopher"
},
{
"family_name": "Alford",
"given_name": "Mark G.",
"orcid": "0000-0001-9675-7005",
"clpid": "Alford-Mark-G"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272",
"clpid": "Noronha-Jorge"
},
{
"family_name": "Noronha-Hostler",
"given_name": "Jacquelyn",
"orcid": "0000-0003-3229-4958",
"clpid": "Noronha-Hostler-Jacquelyn"
},
{
"family_name": "Pretorius",
"given_name": "Frans",
"orcid": "0000-0001-8399-2217",
"clpid": "Pretorius-Frans"
},
{
"family_name": "Witek",
"given_name": "Helvi",
"orcid": "0000-0003-3043-163X",
"clpid": "Witek-Helvi"
},
{
"family_name": "Yunes",
"given_name": "Nicol\u00e1s",
"orcid": "0000-0001-6147-1736",
"clpid": "Yunes-Nicol\u00e1s"
}
],
"abstract": "In this work, we estimate how much bulk viscosity driven by Urca processes is likely to affect the gravitational wave signal of a neutron star coalescence. In the late inspiral, we show that bulk viscosity affects the binding energy at fourth post-Newtonian order. Even though this effect is enhanced by the square of the gravitational compactness, the coefficient of bulk viscosity is likely too small to lead to observable effects in the waveform during the late inspiral, when only considering the orbital motion itself. In the post-merger, however, the characteristic time-scales and spatial scales are different, potentially leading to the opposite conclusion. We post-process data from a state-of-the-art equal-mass binary neutron star merger simulation to estimate the effects of bulk viscosity (which was not included in the simulation itself). In that scenario, we find that bulk viscosity can reach high values in regions of the merger. We compute several estimates of how much it might directly affect the global dynamics of the considered merger scenario, and find that it could become significant. Even larger effects could arise in different merger scenarios or in simulations that include non-linear effects. This assessment is reinforced by a quantitative comparison with relativistic heavy-ion collisions where such effects have been explored extensively.",
"doi": "10.1093/mnras/stab2793",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2022-01",
"series_number": "1",
"volume": "509",
"issue": "1",
"pages": "1096-1108"
},
{
"id": "authors:scv0c-83z32",
"collection": "authors",
"collection_id": "scv0c-83z32",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297065000.26",
"type": "article",
"title": "Impact of the nuclear symmetry energy on the post-merger phase of a binary neutron star coalescence",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Raithel",
"given_name": "Carolyn A.",
"orcid": "0000-0002-1798-6668",
"clpid": "Raithel-Carolyn-A"
}
],
"abstract": "The nuclear symmetry energy plays a key role in determining the equation of state of dense, neutron-rich matter, which governs the properties of both terrestrial nuclear matter as well as astrophysical neutron stars. A recent measurement of the neutron skin thickness from the PREX Collaboration has lead to new constraints on the slope of the nuclear symmetry energy, L, which can be directly compared to inferences from gravitational wave observations of the first binary neutron star merger inspiral, GW170817. In this paper, we explore a new regime for potentially constraining the slope, L, of the nuclear symmetry energy with future gravitational wave events: the post-merger phase of a binary neutron star coalescence. In particular, we go beyond the inspiral phase, where imprints of the slope parameter L may be inferred from measurements of the tidal deformability, to consider imprints on the post-merger dynamics, gravitational wave emission, and dynamical mass ejection. To this end, we perform a set of targeted neutron star merger simulations in full general relativity using new finite-temperature equations of state, which systematically vary L while keeping the magnitude of the symmetry energy at the saturation density, S, fixed. We find that the post-merger dynamics and gravitational wave emission are mostly insensitive to the slope of the nuclear symmetry energy. In contrast, we find that dynamical mass ejection contains a weak imprint of L, with large values of L leading to systematically enhanced ejecta.",
"doi": "10.1103/physrevd.104.124012",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2021-12-15",
"series_number": "12",
"volume": "104",
"issue": "12",
"pages": "Art. No. 124012"
},
{
"id": "authors:57eyx-40420",
"collection": "authors",
"collection_id": "57eyx-40420",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297185000.35",
"type": "article",
"title": "Weak Alfv\u00e9nic turbulence in relativistic plasmas. Part 1. Dynamical equations and basic dynamics of interacting resonant triads",
"author": [
{
"family_name": "TenBarge",
"given_name": "J. M.",
"orcid": "0000-0003-0143-951X",
"clpid": "TenBarge-Jason-M"
},
{
"family_name": "Ripperda",
"given_name": "B.",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Bart"
},
{
"family_name": "Chernoglazov",
"given_name": "A.",
"orcid": "0000-0001-5121-1594",
"clpid": "Chernoglazov-Alexander"
},
{
"family_name": "Bhattacharjee",
"given_name": "A.",
"clpid": "Bhattacharjee-A"
},
{
"family_name": "Mahlmann",
"given_name": "J. F.",
"orcid": "0000-0002-5349-7116",
"clpid": "Mahlmann-Jens-Florian"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Juno",
"given_name": "J.",
"orcid": "0000-0001-6835-273X",
"clpid": "Juno-James"
},
{
"family_name": "Yuan",
"given_name": "Y.",
"orcid": "0000-0002-0108-4774",
"clpid": "Yuan-Yajie"
},
{
"family_name": "Philippov",
"given_name": "A. A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
}
],
"abstract": "Alfv\u00e9n wave collisions are the primary building blocks of the non-relativistic turbulence that permeates the heliosphere and low- to moderate-energy astrophysical systems. However, many astrophysical systems such as gamma-ray bursts, pulsar and magnetar magnetospheres and active galactic nuclei have relativistic flows or energy densities. To better understand these high-energy systems, we derive reduced relativistic magnetohydrodynamics equations and employ them to examine weak Alfv\u00e9nic turbulence, dominated by three-wave interactions, in reduced relativistic magnetohydrodynamics, including the force-free, infinitely magnetized limit. We compare both numerical and analytical solutions to demonstrate that many of the findings from non-relativistic weak turbulence are retained in relativistic systems. But, an important distinction in the relativistic limit is the inapplicability of a formally incompressible limit, i.e. there exists finite coupling to the compressible fast mode regardless of the strength of the magnetic field. Since fast modes can propagate across field lines, this mechanism provides a route for energy to escape strongly magnetized systems, e.g. magnetar magnetospheres. However, we find that the fast-Alfv\u00e9n coupling is diminished in the limit of oblique propagation.",
"doi": "10.1017/s002237782100115x",
"issn": "0022-3778",
"publisher": "Cambridge University Press",
"publication": "Journal of Plasma Physics",
"publication_date": "2021-12",
"series_number": "6",
"volume": "87",
"issue": "6",
"pages": "Art. No. 905870614"
},
{
"id": "authors:8b0p5-6ns61",
"collection": "authors",
"collection_id": "8b0p5-6ns61",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297157000.32",
"type": "article",
"title": "Quasi-universal Behavior of the Threshold Mass in Unequal-mass, Spinning Binary Neutron Star Mergers",
"author": [
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Paperfort-Ludwig-Jens"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The lifetime of the remnant produced by the merger of two neutron stars can provide a wealth of information on the equation of state of nuclear matter and on the processes leading to the electromagnetic counterpart. Hence, it is essential to determine when this lifetime is the shortest, corresponding to when the remnant has a mass equal to the threshold mass, M\u209c\u2095, to prompt collapse to a black hole. We report on the results of more than 360 simulations of merging neutron-star binaries covering 40 different configurations differing in mass ratio and spin of the primary. Using this data, we have derived a quasi-universal relation for M\u209c\u2095 and expressed its dependence on the mass ratio and spin of the binary. The new expression recovers the results of Koeppel et al. for equal-mass, irrotational binaries and reveals that M\u209c\u2095 can increase (decrease) by 5% (10%) for binaries that have spins aligned (antialigned) with the orbital angular momentum and provides evidence for a nonmonotonic dependence of M\u209c\u2095 on the mass asymmetry in the system. Finally, we extend to unequal masses and spinning binaries the lower limits that can be set on the stellar radii once a neutron star binary is detected, illustrating how the merger of an unequal-mass, rapidly spinning binary can significantly constrain the allowed values of the stellar radii.",
"doi": "10.3847/2041-8213/ac350d",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2021-11-20",
"series_number": "1",
"volume": "922",
"issue": "1",
"pages": "Art. No. L19"
},
{
"id": "authors:8v3jx-5vx19",
"collection": "authors",
"collection_id": "8v3jx-5vx19",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297074000.27",
"type": "article",
"title": "Dissipative magnetohydrodynamics for nonresistive relativistic plasmas: An implicit second-order flux-conservative formulation with stiff relaxation",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Noronha",
"given_name": "Jorge",
"orcid": "0000-0002-9817-0272",
"clpid": "Noronha-Jorge"
}
],
"abstract": "Based on a 14-moment closure for nonresistive (general-) relativistic viscous plasmas, we describe a new numerical scheme that is able to handle all first-order dissipative effects (heat conduction, bulk and shear viscosities), as well the anisotropies induced by the presence of magnetic fields. The latter is parametrized in terms of a thermal gyrofrequency or, equivalently, a thermal Larmor radius and allows to correctly capture the thermal Hall effect. By solving an extended Israel-Stewart-like system for the dissipative quantities that enforces algebraic constraints via stiff-relaxation, we are able to cast all first-order dissipative terms in flux-divergence form. This allows us to apply traditional high-resolution shock capturing methods to the equations, making the system suitable for the numerical study of highly turbulent flows. We present several numerical tests to assess the robustness of our numerical scheme in flat spacetime. The 14-moment closure can seamlessly interpolate between the highly collisional limit found in neutron star mergers, and the highly anisotropic limit of relativistic Braginskii magnetohydrodynamics appropriate for weakly collisional plasmas in black-hole accretion problems. We believe that this new formulation and numerical scheme will be useful for a broad class of relativistic magnetized flows.",
"doi": "10.1103/physrevd.104.103028",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2021-11-15",
"series_number": "10",
"volume": "104",
"issue": "10",
"pages": "Art. No. 103028"
},
{
"id": "authors:y3tmv-nrz29",
"collection": "authors",
"collection_id": "y3tmv-nrz29",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297175000.34",
"type": "article",
"title": "Scaling of Small-scale Dynamo Properties in the Rayleigh-Taylor Instability",
"author": [
{
"family_name": "Skoutnev",
"given_name": "V.",
"orcid": "0000-0001-5287-498X",
"clpid": "Skoutnev-Valentin"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Bhattacharjee",
"given_name": "A.",
"clpid": "Bhattacharjee-A"
},
{
"family_name": "Philippov",
"given_name": "A. A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
}
],
"abstract": "We derive scaling relations based on freefall and isotropy assumptions for the kinematic small-scale dynamo growth rate and amplification factor over the course of the mixing, saturation, and decay phases of the Rayleigh\u2013Taylor instability (RTI) in a fully ionized plasma. The scaling relations are tested using sets of three-dimensional, visco-resistive MHD simulations of the RTI. They are found to hold in the saturation phase, but exhibit discrepancies during the mixing and decay phases, suggesting a need to relax either the freefall or isotropy assumptions. Application of the scaling relations allows for quantitative prediction of the net amplification of magnetic energy in the kinematic dynamo phase and therefore a determination of whether the magnetic energy either remains sub-equipartition at all velocity scales or reaches equipartition with at least some scales of the turbulent kinetic energy in laboratory and astrophysical scenarios. As an example, we consider the dynamo in RTI-unstable regions of the outer envelope of a binary neutron star merger, and predict that the kinematic regime of the small-scale dynamo ends on the timescale of nanoseconds and then reaches saturation on a timescale of microseconds, which are both fast compared to the millisecond relaxation time of the post-merger.",
"doi": "10.3847/1538-4357/ac1ba4",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2021-11-01",
"series_number": "1",
"volume": "921",
"issue": "1",
"pages": "Art. No. 75"
},
{
"id": "authors:3arjw-pv397",
"collection": "authors",
"collection_id": "3arjw-pv397",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297226000.37",
"type": "article",
"title": "Weak Alfv\u00e9nic turbulence in relativistic plasmas.\nPart 2. current sheets and dissipation",
"author": [
{
"family_name": "Ripperda",
"given_name": "B.",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Barrt"
},
{
"family_name": "Mahlmann",
"given_name": "J. F.",
"orcid": "0000-0002-5349-7116",
"clpid": "Mahlmann-Jens-Florian"
},
{
"family_name": "Chernoglazov",
"given_name": "A.",
"orcid": "0000-0001-5121-1594",
"clpid": "Chernoglazov-Alexander"
},
{
"family_name": "TenBarge",
"given_name": "J. M.",
"orcid": "0000-0003-0143-951X",
"clpid": "TenBarge-Jason-M"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Juno",
"given_name": "J.",
"orcid": "0000-0001-6835-273X",
"clpid": "Juno-James"
},
{
"family_name": "Philippov",
"given_name": "A. A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
},
{
"family_name": "Bhattacharjee",
"given_name": "A.",
"clpid": "Bhattacharjee-A"
}
],
"abstract": "Alfv\u00e9n waves as excited in black hole accretion disks and neutron star magnetospheres are the building blocks of turbulence in relativistic, magnetized plasmas. A large reservoir of magnetic energy is available in these systems, such that the plasma can be heated significantly even in the weak turbulence regime. We perform high-resolution three-dimensional simulations of counter-propagating Alfv\u00e9n waves, showing that an E_(B\u22a5) (k_\u22a5) \u221d (k\u207b\u00b2)_\u22a5energy spectrum develops as a result of the weak turbulence cascade in relativistic magnetohydrodynamics and its infinitely magnetized (force-free) limit. The plasma turbulence ubiquitously generates current sheets, which act as locations where magnetic energy dissipates. We show that current sheets form as a natural result of nonlinear interactions between counter-propagating Alfv\u00e9n waves. These current sheets form owing to the compression of elongated eddies, driven by the shear induced by growing higher-order modes, and undergo a thinning process until they break-up into small-scale turbulent structures. We explore the formation of current sheets both in overlapping waves and in localized wave packet collisions. The relativistic interaction of localized Alfv\u00e9n waves induces both Alfv\u00e9n waves and fast waves, and efficiently mediates the conversion and dissipation of electromagnetic energy in astrophysical systems. Plasma energization through reconnection in current sheets emerging during the interaction of Alfv\u00e9n waves can potentially explain X-ray emission in black hole accretion coronae and neutron star magnetospheres.",
"doi": "10.1017/s0022377821000957",
"issn": "0022-3778",
"publisher": "Cambridge University Press",
"publication": "Journal of Plasma Physics",
"publication_date": "2021-10",
"series_number": "5",
"volume": "87",
"issue": "5",
"pages": "Art. No. 905870512"
},
{
"id": "authors:6ykyx-1mm10",
"collection": "authors",
"collection_id": "6ykyx-1mm10",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297238000.38",
"type": "article",
"title": "On accretion discs formed in MHD simulations of black hole\u2013neutron star mergers with accurate microphysics",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "Remnant accretion discs formed in compact object mergers are an important ingredient in the understanding of electromagnetic afterglows of multimessenger gravitational-wave events. Due to magnetically and neutrino-driven winds, a significant fraction of the disc mass will eventually become unbound and undergo r-process nucleosynthesis. While this process has been studied in some detail, previous studies have typically used approximate initial conditions for the accretion discs, or started from purely hydrodynamical simulations. In this work, we analyse the properties of accretion discs formed from near equal-mass black hole\u2013neutron star mergers simulated in general-relativistic magnetohydrodynamics in dynamical spacetimes with an accurate microphysical description. The post-merger systems were evolved until 120 ms for different finite-temperature equations of state and black hole spins. We present a detailed analysis of the fluid properties and of the magnetic-field topology. In particular, we provide analytic fits of the magnetic-field strength and specific entropy as a function of the rest-mass density, which can be used for the construction of equilibrium disc models. Finally, we evolve one of the systems for a total of 350 ms after merger and study the prospect for eventual jet launching. While our simulations do not reach this stage, we find clear evidence of continued funnel magnetization and clearing, a prerequisite for any jet-launching mechanism.",
"doi": "10.1093/mnras/stab1824",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2021-09",
"series_number": "3",
"volume": "506",
"issue": "3",
"pages": "3511-3526"
},
{
"id": "authors:6v9pz-s5051",
"collection": "authors",
"collection_id": "6v9pz-s5051",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297257000.40",
"type": "article",
"title": "New public code for initial data of unequal-mass, spinning compact-object binaries",
"author": [
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Grandcl\u00e9ment",
"given_name": "Philippe",
"orcid": "0000-0001-6807-7387",
"clpid": "Grandcl\u00e9ment-Philippe"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The construction of constraint-satisfying initial data is an essential element for the numerical exploration of the dynamics of compact-object binaries. While several codes have been developed over the years to compute generic quasiequilibrium configurations of binaries comprising either two black holes, or two neutron stars, or a black hole and a neutron star, these codes are often not publicly available or they provide only a limited capability in terms of mass ratios and spins of the components in the binary. We here present a new open-source collection of spectral elliptic solvers that are capable of exploring the major parameter space of binary black holes (BBHs), binary neutron stars (BNSs), and mixed binaries of black holes and neutron stars (BHNSs). Particularly important is the ability of the spectral-solver library to handle neutron stars that are either irrotational or with an intrinsic spin angular momentum that is parallel to the orbital one. By supporting both analytic and tabulated equations of state at zero or finite temperature, the new infrastructure is particularly geared toward allowing for the construction of BHNS and BNS binaries. For the latter, we show that the new solvers are able to reach the most extreme corners in the physically plausible space of parameters, including extreme mass ratios and spin asymmetries, thus representing the most extreme BNS computed to date. Through a systematic series of examples, we demonstrate that the solvers are able to construct quasiequilibrium and eccentricity-reduced initial data for BBHs, BNSs, and BHNSs, achieving spectral convergence in all cases. Furthermore, using such initial data, we have carried out evolutions of these systems from the inspiral to after the merger, obtaining evolutions with eccentricities \u2272 10\u207b\u2074\u221210\u207b\u00b3, and accurate gravitational waveforms.",
"doi": "10.1103/physrevd.104.024057",
"issn": "2470-0010",
"publisher": "American Physical Society",
"publication": "Physical Review D",
"publication_date": "2021-07-15",
"series_number": "2",
"volume": "104",
"issue": "2",
"pages": "Art. No. 024057"
},
{
"id": "authors:t2g60-60356",
"collection": "authors",
"collection_id": "t2g60-60356",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297283000.42",
"type": "article",
"title": "Fast Ejecta as a Potential Way to Distinguish Black Holes from Neutron Stars in High-mass Gravitational-wave Events",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Tootle",
"given_name": "Samuel D.",
"orcid": "0000-0001-9781-0496",
"clpid": "Tootle-Samuel-D"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "High-mass gravitational-wave events in the neutron-star mass range, such as GW190425, have recently started to be detected by the LIGO/Virgo detectors. If the masses of the two binary components fall in the neutron-star mass range, such a system is typically classified as a binary neutron-star system, although the detected gravitational-wave signal may be too noisy to clearly establish a neutron-star nature of the high-mass component in the binary and rule out a black hole\u2013neutron star system for such an event. We show that high-mass binary neutron-star mergers with a very massive neutron-star primary close to the maximum-mass limit, m\u2081 \u2273 2.2 M_\u2299, produce fast dynamical mass ejecta from the spin-up of the primary star at merger. By simulating the merger of black hole\u2013neutron star systems of exactly the same masses and spins, we show that these fast ejecta are entirely absent if the primary is instead a black hole. In addition, we find that both systems leave almost identical amounts of baryon mass behind, which is not immediately accreted by the black hole. This implies that both systems will likely have comparable electromagnetic afterglow emission stemming from the remnant disk. Hence, fast ejecta at merger have the potential to distinguish neutron stars from black holes in high-mass mergers, although these ejecta may be challenging to detect observationally.",
"doi": "10.3847/1538-4357/abf0a5",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2021-05-01",
"series_number": "1",
"volume": "912",
"issue": "1",
"pages": "Art. No. 80"
},
{
"id": "authors:yyxr2-s2613",
"collection": "authors",
"collection_id": "yyxr2-s2613",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297335000.43",
"type": "article",
"title": "GW170817 and GW190814: Tension on the Maximum Mass",
"author": [
{
"family_name": "Nathanail",
"given_name": "Antonios",
"clpid": "Nathanail-Antnios"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The detection of the binary events GW170817 and GW190814 has provided invaluable constraints on the maximum mass of nonrotating configurations of neutron stars, M_(TOV). However, the large differences in the neutron-star masses measured in GW170817 and GW190814 has also lead to significant tension between the predictions for such maximum masses, with GW170817 suggesting that M_(TOV) \u2272 2.3 M_\u2299, and GW190814 requiring M_(TOV) \u2273 2.5 M_\u2299 if the secondary was a (non- or slowly rotating) neutron star at merger. Using a genetic algorithm, we sample the multidimensional space of parameters spanned by gravitational-wave and astronomical observations associated with GW170817. Consistent with previous estimates, we find that all of the physical quantities are in agreement with the observations if the maximum mass is in the range of M_(TOV)_(-0.123)^(0.116) M_\u2299 within a 2\u03c3 confidence level. By contrast, maximum masses with M_(TOV) \u2273 2.5 M_\u2299, not only require efficiencies in the gravitational-wave emission that are well above the numerical-relativity estimates, but they also lead to a significant underproduction of the ejected mass. Hence, the tension can be released by assuming that the secondary in GW190814 was a black hole at merger, although it could have been a rotating neutron star before.",
"doi": "10.3847/2041-8213/abdfc6",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2021-02-20",
"series_number": "2",
"volume": "908",
"issue": "2",
"pages": "Art. No. L28"
},
{
"id": "authors:8nywn-ssa82",
"collection": "authors",
"collection_id": "8nywn-ssa82",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297342000.44",
"type": "article",
"title": "A lower bound on the maximum mass if the secondary in GW190814 was once a rapidly spinning neutron star",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Weih",
"given_name": "Lukas R.",
"orcid": "0000-0002-9608-8689",
"clpid": "Weih-Lukas-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The recent detection of GW190814 featured the merger of a binary with a primary having a mass of \u223c23 M_\u2299 and a secondary with a mass of \u223c2.6 M_\u2299\u2060. While the primary was most likely a black hole, the secondary could be interpreted as either the lightest black hole or the most massive neutron star ever observed, but also as the indication of a novel class of exotic compact objects. We here argue that although the secondary in GW190814 is most likely a black hole at merger, it needs not be an ab-initio black hole nor an exotic object. Rather, based on our current understanding of the nuclear-matter equation of state, it can be a rapidly rotating neutron star that collapsed to a rotating black hole at some point before merger. Using universal relations connecting the masses and spins of uniformly rotating neutron stars, we estimate the spin, 0.49^(+0.08)_(\u22120.05) \u2272 \u03c7 \u2272 0.68^(+0.11)_(\u22120.05)\u2060, of the secondary \u2013 a quantity not constrained so far by the detection \u2013 and a novel strict lower bound on the maximum mass, M_(TOV) > 2.08^(+0.04)_(\u22120.04) M_\u2299 and an optimal bound of M_(TOV) > 2.15^(+0.04)_(\u22120.04) M_\u2299\u2060, of non-rotating neutron stars, consistent with recent observations of a very massive pulsar. The new lower bound also remains valid even in the less likely scenario in which the secondary neutron star never collapsed to a black hole.",
"doi": "10.1093/mnrasl/slaa168",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2020-11",
"series_number": "1",
"volume": "499",
"issue": "1",
"pages": "L82-L86"
},
{
"id": "authors:840e0-h5d30",
"collection": "authors",
"collection_id": "840e0-h5d30",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297378000.46",
"type": "article",
"title": "Electromagnetic Precursors to Gravitational-wave Events: Numerical Simulations of Flaring in Pre-merger Binary Neutron Star Magnetospheres",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Philippov",
"given_name": "Alexander A.",
"orcid": "0000-0001-7801-0362",
"clpid": "Philippov-Alexander-A"
}
],
"abstract": "The detection of gravitational waves from neutron star merger events has opened up a new field of multimessenger astronomy linking gravitational-wave events to short gamma-ray bursts and kilonova afterglows. A further\u2014yet to be discovered\u2014electromagnetic counterpart is a precursor emission produced by the nontrivial interaction of the magnetospheres of the two neutron stars prior to merger. By performing special-relativistic force-free simulations of orbiting neutron stars we discuss the effect of different magnetic field orientations and show how the emission can be significantly enhanced by differential motion present in the binary, either due to stellar spins or misaligned stellar magnetospheres. We find that the buildup of twist in the magnetic flux tube connecting the two stars can lead to the repeated emission of powerful flares for a variety of orbital configurations. We also discuss potential coherent radio emission mechanisms in the flaring process.",
"doi": "10.3847/2041-8213/ab8196",
"issn": "2041-8213",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2020-04-10",
"series_number": "1",
"volume": "893",
"issue": "1",
"pages": "Art. No. L6"
},
{
"id": "authors:57wqk-tzs71",
"collection": "authors",
"collection_id": "57wqk-tzs71",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297392000.47",
"type": "article",
"title": "On the deconfinement phase transition in neutron-star mergers",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jena"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Stoecker",
"given_name": "Horst",
"orcid": "0000-0002-3282-3664",
"clpid": "Stoecker-Horst"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "We study in detail the nuclear aspects of a neutron-star merger in which deconfinement to quark matter takes place. For this purpose, we make use of the Chiral Mean Field (CMF) model, an effective relativistic model that includes self-consistent chiral symmetry restoration and deconfinement to quark matter and, for this reason, predicts the existence of different degrees of freedom depending on the local density/chemical potential and temperature. We then use the out-of-chemical-equilibrium finite-temperature CMF equation of state in full general-relativistic simulations to analyze which regions of different QCD phase diagrams are probed and which conditions, such as strangeness and entropy, are generated when a strong first-order phase transition appears. We also investigate the amount of electrons present in different stages of the merger and discuss how far from chemical equilibrium they can be and, finally, draw some comparisons with matter created in supernova explosions and heavy-ion collisions.",
"doi": "10.1140/epja/s10050-020-00073-4",
"issn": "1434-6001",
"publisher": "Springer",
"publication": "European Physical Journal A: Hadrons and Nuclei",
"publication_date": "2020-02",
"series_number": "2",
"volume": "56",
"issue": "2",
"pages": "Art. No. 59"
},
{
"id": "authors:0npam-9yd09",
"collection": "authors",
"collection_id": "0npam-9yd09",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297415000.49",
"type": "article",
"title": "Beyond second-order convergence in simulations of magnetized binary neutron stars with realistic microphysics",
"author": [
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Rezzolla",
"given_name": "L.",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "We investigate the impact of using high-order numerical methods to study the merger of magnetized neutron stars with finite-temperature microphysics and neutrino cooling in full general relativity. By implementing a fourth-order accurate conservative finite-difference scheme we model the inspiral together with the early post-merger and highlight the differences to traditional second-order approaches at the various stages of the simulation. We find that even for finite-temperature equations of state, convergence orders higher than second order can be achieved in the inspiral and post-merger for the gravitational-wave phase. We further demonstrate that the second-order scheme overestimates the amount of proton-rich shock-heated ejecta, which can have an impact on the modelling of the dynamical part of the kilonova emission. Finally, we show that already at low resolution the growth rate of the magnetic energy is consistently resolved by using a fourth-order scheme.",
"doi": "10.1093/mnras/stz2809",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2019-12",
"series_number": "3",
"volume": "490",
"issue": "3",
"pages": "3588-3600"
},
{
"id": "authors:t9bz3-8wc80",
"collection": "authors",
"collection_id": "t9bz3-8wc80",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297425000.51",
"type": "article",
"title": "Impact of High Spins on the Ejection of Mass in GW170817",
"author": [
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. J.",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Tsokaros",
"given_name": "A.",
"orcid": "0000-0003-2242-8924",
"clpid": "Tsokaros-Antonios"
},
{
"family_name": "Rezzolla",
"given_name": "L.",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "Following the detection of GW170817 and the accompanying kilonova AT 2017gfo, it has become crucial to model and understand the various channels through which mass is ejected in neutron-star binary mergers. We discuss the impact that high stellar spins prior to merger have on the ejection of mass focusing, in particular, on the dynamically ejected mass by performing general-relativistic magnetohydrodynamic simulations employing finite-temperature equations of state and neutrino-cooling effects. Using eight different models with dimensionless spins ranging from \u03c7 \u2243 -0.14 to \u03c7 \u2243 0.29 we discuss how the presence of different spins affects the angular distribution and composition of the ejected matter. Most importantly, we find that the dynamical component of the ejected mass can be strongly suppressed in the case of high spins aligned with the orbital angular momentum. In this case, in fact, the merger remnant has an excess angular momentum yielding a more extended and \"colder\" object, with reduced ability to shed mass dynamically. We discuss how this result impacts the analysis of the recent merger event GW170817 and its kilonova afterglow.",
"doi": "10.3847/1538-4357/ab3ebb",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-10-10",
"series_number": "1",
"volume": "884",
"issue": "1",
"pages": "Art. No. 40"
},
{
"id": "authors:twa7n-e9t19",
"collection": "authors",
"collection_id": "twa7n-e9t19",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297488000.53",
"type": "article",
"title": "Constrained transport and adaptive mesh refinement in the Black Hole Accretion Code",
"author": [
{
"family_name": "Olivares",
"given_name": "Hector",
"orcid": "0000-0001-6833-7580",
"clpid": "olivares-H\u00e9ctor"
},
{
"family_name": "Porth",
"given_name": "Oliver",
"orcid": "0000-0002-4584-2557",
"clpid": "Porth-Oliver"
},
{
"family_name": "Davelaar",
"given_name": "Jordy",
"orcid": "0000-0002-2685-2434",
"clpid": "Davelaar-Jordy"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Fromm",
"given_name": "Christian M.",
"orcid": "0000-0002-1827-1656",
"clpid": "Fromm-Christian-M"
},
{
"family_name": "Mizuno",
"given_name": "Yosuke",
"orcid": "0000-0002-8131-6730",
"clpid": "Mizuno-Yosuke"
},
{
"family_name": "Younsi",
"given_name": "Ziri",
"orcid": "0000-0001-9283-1191",
"clpid": "Younsi-Ziri"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "Context. Worldwide very long baseline radio interferometry (VLBI) arrays are expected to obtain horizon-scale images of supermassive black hole candidates and of relativistic jets in several nearby active galactic nuclei. This, together with the expected detection of electromagnetic counterparts of gravitational-wave signals, motivates the development of models for magnetohydrodynamic flows in strong gravitational fields. \n\nAims. The Black Hole Accretion Code (BHAC) is a publicliy available code intended to aid with the modeling of such sources by performing general relativistic magnetohydrodynamical simulations in arbitrary stationary spacetimes. New additions to the code are required in order to guarantee an accurate evolution of the magnetic field when small and large scales are captured simultaneously. \n\nMethods. We discuss the adaptive mesh refinement (AMR) techniques employed in BHAC, which are essential to keep several problems computationally tractable, as well as staggered-mesh-based constrained transport (CT) algorithms to preserve the divergence-free constraint of the magnetic field. We also present a general class of prolongation operators for face-allocated variables compatible with them. \n\nResults. After presenting several standard tests for the new implementation, we show that the choice of the divergence-control method can produce qualitative differences in the simulation results for scientifically relevant accretion problems. We demonstrate the ability of AMR to decrease the computational costs of black hole accretion simulations while sufficiently resolving turbulence arising from the magnetorotational instability. In particular, we describe a simulation of an accreting Kerr black hole in Cartesian coordinates using AMR to follow the propagation of a relativistic jet while self-consistently including the jet engine, a problem set up for which the new AMR implementation is particularly advantageous. \n\nConclusions. The CT methods and AMR strategies discussed here are currently being used in the simulations performed with BHAC for the generation of theoretical models for the Event Horizon Telescope collaboration.",
"doi": "10.1051/0004-6361/201935559",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2019-09",
"volume": "629",
"pages": "Art. No. A61"
},
{
"id": "authors:5fyj5-vvt08",
"collection": "authors",
"collection_id": "5fyj5-vvt08",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297430000.52",
"type": "article",
"title": "General-relativistic Resistive Magnetohydrodynamics with Robust Primitive-variable Recovery for Accretion Disk Simulations",
"author": [
{
"family_name": "Ripperda",
"given_name": "B.",
"orcid": "0000-0002-7301-3908",
"clpid": "Ripperda-Bart"
},
{
"family_name": "Bacchini",
"given_name": "F.",
"orcid": "0000-0002-7526-8154",
"clpid": "Bacchini-Fabio"
},
{
"family_name": "Porth",
"given_name": "O.",
"orcid": "0000-0002-4584-2557",
"clpid": "Porth-Oliver"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Olivares",
"given_name": "H.",
"orcid": "0000-0001-6833-7580",
"clpid": "Olivares-H\u00e9ctor"
},
{
"family_name": "Nathanail",
"given_name": "A.",
"clpid": "Nathanail-Antonios"
},
{
"family_name": "Rezzolla",
"given_name": "L.",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
},
{
"family_name": "Teunissen",
"given_name": "J.",
"orcid": "0000-0003-0811-5091",
"clpid": "Teunissen-Jannis"
},
{
"family_name": "Keppens",
"given_name": "R.",
"orcid": "0000-0003-3544-2733",
"clpid": "Keppens-Rory"
}
],
"abstract": "Recent advances in black hole astrophysics, particularly the first visual evidence of a supermassive black hole at the center of the galaxy M87 by the Event Horizon Telescope, and the detection of an orbiting \"hot spot\" nearby the event horizon of Sgr A* in the Galactic center by the Gravity Collaboration, require the development of novel numerical methods to understand the underlying plasma microphysics. Non-thermal emission related to such hot spots is conjectured to originate from plasmoids that form due to magnetic reconnection in thin current layers in the innermost accretion zone. Resistivity plays a crucial role in current sheet formation, magnetic reconnection, and plasmoid growth in black hole accretion disks and jets. We included resistivity in the three-dimensional general-relativistic magnetohydrodynamics (GRMHD) code BHAC and present the implementation of an implicit\u2013explicit scheme to treat the stiff resistive source terms of the GRMHD equations. The algorithm is tested in combination with adaptive mesh refinement to resolve the resistive scales and a constrained transport method to keep the magnetic field solenoidal. Several novel methods for primitive-variable recovery, a key part in relativistic magnetohydrodynamics codes, are presented and compared for accuracy, robustness, and efficiency. We propose a new inversion strategy that allows for resistive-GRMHD simulations of low gas-to-magnetic pressure ratio and highly magnetized regimes as applicable for black hole accretion disks, jets, and neutron-star magnetospheres. We apply the new scheme to study the effect of resistivity on accreting black holes, accounting for dissipative effects as reconnection.",
"doi": "10.3847/1538-4365/ab3922",
"issn": "1538-4365",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Supplement Series",
"publication_date": "2019-09",
"series_number": "1",
"volume": "244",
"issue": "1",
"pages": "Art. No. 10"
},
{
"id": "authors:4fazm-a0a05",
"collection": "authors",
"collection_id": "4fazm-a0a05",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297531000.55",
"type": "article",
"title": "Optimal Neutron-star Mass Ranges to Constrain the Equation of State of Nuclear Matter with Electromagnetic and Gravitational-wave Observations",
"author": [
{
"family_name": "Weih",
"given_name": "L. R.",
"orcid": "0000-0002-9608-8689",
"clpid": "Weih-Lukas-R"
},
{
"family_name": "Most",
"given_name": "E. R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "L.",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "Exploiting a very large library of physically plausible equations of state (EOSs) containing more than 107 members and yielding more than 109 stellar models, we conduct a survey of the impact that a neutron-star radius measurement via electromagnetic observations can have on the EOS of nuclear matter. Such measurements are soon to be expected from the ongoing Neutron Star Interior Composition Explorer mission and will complement the constraints on the EOS from gravitational-wave detections. Thanks to the large statistical range of our EOS library, we can obtain a first quantitative estimate of the commonly made assumption that the high-density part of the EOS is best constrained when measuring the radius of the most massive, albeit rare, neutron stars with masses M\u00a0\u2273\u00a02.1 M_\u2299. At the same time, we find that radius measurements of neutron stars with masses M\u00a0\u2243\u00a01.7\u20131.85 M_\u2299 can provide the strongest constraints on the low-density part of the EOS. Finally, we quantify how radius measurements by future missions can further improve our understanding of the EOS of matter at nuclear densities.",
"doi": "10.3847/1538-4357/ab2edd",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2019-08-10",
"series_number": "1",
"volume": "881",
"issue": "1",
"pages": "Art. No. 73"
},
{
"id": "authors:hr79x-9ja05",
"collection": "authors",
"collection_id": "hr79x-9ja05",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-434610000.3",
"type": "article",
"title": "MAGIC - how MAtter's extreme phases can be revealed in Gravitational wave observations and in relativistic heavy Ion Collision experiments",
"author": [
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Bovard",
"given_name": "Luke",
"orcid": "0000-0003-3555-062X",
"clpid": "Bovard-Luke"
},
{
"family_name": "Steinheimer",
"given_name": "Jan",
"orcid": "0000-0003-2565-7503",
"clpid": "Steinheimer-Jan"
},
{
"family_name": "Motornenko",
"given_name": "Anton",
"orcid": "0000-0003-3037-9923",
"clpid": "Motornenko-Anton"
},
{
"family_name": "Vovchenko",
"given_name": "Volodymyr",
"orcid": "0000-0002-2189-4766",
"clpid": "Vovchenko-Volodymyr"
},
{
"family_name": "Schramm",
"given_name": "Stefan",
"clpid": "Schramm-Stefan"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Papenfort",
"given_name": "Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "St\u00f6cker",
"given_name": "Horst",
"orcid": "0000-0002-4028-0532",
"clpid": "St\u00f6cker-Horst"
}
],
"abstract": "Nearly one hundred years after Albert Einstein developed the field equations of general relativity and predicted the existence of gravitational waves, a gravitational wave event from a binary neutron star merger (GW170817) was detected in August 2017 by the LIGO/VIRGO collaboration. During the thereon analysis of the gravitational wave data, the equation of state of elementary matter could be constrained in the regime of high densities/temperatures. Recent simulations show, that the appearance of a hadron to quark phase transition in the interior region of a hybrid star merger remnant might change the overall properties of the merger event and could be detectable in future. On the one hand, 4D-simulations of binary neutron star mergers show that these astrophysical systems represent optimal laboratories to investigate the phase structure of quantum chromodynamics. On the other hand, accelerators like the FAIR facility at GSI Helmholtzzentrum allow one to study the properties of the quark-gluon plasma produced in relativistic collisions of heavy ions. This article combines a survey of recent advancements in two rather distinct fields, which reveal - on first sight - a surprising similarity of both, namely relativistic collisions of nuclei and of neutron star mergers.",
"doi": "10.1088/1742-6596/1271/1/012023",
"issn": "1742-6588",
"publisher": "Institute of Physics",
"publication": "Journal of Physics Conference Series",
"publication_date": "2019-07-26",
"volume": "1271",
"pages": "Art. No. 012023"
},
{
"id": "authors:kykp7-yxy11",
"collection": "authors",
"collection_id": "kykp7-yxy11",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-434554000.2",
"type": "article",
"title": "Detecting the Hadron-Quark Phase Transition with Gravitational Waves",
"author": [
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Bovard",
"given_name": "Luke",
"orcid": "0000-0003-3555-062X",
"clpid": "Bovard-Luke"
},
{
"family_name": "Most",
"given_name": "Elias",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Steinheimer",
"given_name": "Jan",
"orcid": "0000-0003-2565-7503",
"clpid": "Steinheimer-Jan"
},
{
"family_name": "Motornenko",
"given_name": "Anton",
"orcid": "0000-0003-3037-9923",
"clpid": "Motornenko-Anton"
},
{
"family_name": "Vovchenko",
"given_name": "Volodymyr",
"orcid": "0000-0002-2189-4766",
"clpid": "Vovchenko-Volodymyr"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Schramm",
"given_name": "Stefan",
"clpid": "Schramm-Stefan"
},
{
"family_name": "St\u00f6cker",
"given_name": "Horst",
"clpid": "St\u00f6cker-Horst"
}
],
"abstract": "The long-awaited detection of a gravitational wave from the merger of a binary neutron star in August 2017 (GW170817) marks the beginning of the new field of multi-messenger gravitational wave astronomy. By exploiting the extracted tidal deformations of the two neutron stars from the late inspiral phase of GW170817, it is now possible to constrain several global properties of the equation of state of neutron star matter. However, the most interesting part of the high density and temperature regime of the equation of state is solely imprinted in the post-merger gravitational wave emission from the remnant hypermassive/supramassive neutron star. This regime was not observed in GW170817, but will possibly be detected in forthcoming events within the current observing run of the LIGO/VIRGO collaboration. Numerous numerical-relativity simulations of merging neutron star binaries have been performed during the last decades, and the emitted gravitational wave profiles and the interior structure of the generated remnants have been analysed in detail. The consequences of a potential appearance of a hadron-quark phase transition in the interior region of the produced hypermassive neutron star and the evolution of its underlying matter in the phase diagram of quantum cromo dynamics will be in the focus of this article. It will be shown that the different density/temperature regions of the equation of state can be severely constrained by a measurement of the spectral properties of the emitted post-merger gravitational wave signal from a future binary compact star merger event.",
"doi": "10.3390/universe5060156",
"issn": "2218-1997",
"publisher": "MDPI",
"publication": "Universe",
"publication_date": "2019-06",
"series_number": "6",
"volume": "5",
"issue": "6",
"pages": "Art. No. 156"
},
{
"id": "authors:t9p2q-ebp50",
"collection": "authors",
"collection_id": "t9p2q-ebp50",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-434224000.1",
"type": "article",
"title": "Neutron-Star-Merger Equation of State",
"author": [
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Constantinou",
"given_name": "Constantinos",
"orcid": "0000-0002-4932-0879",
"clpid": "Constantinou-Constantinos"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Schramm",
"given_name": "Stefan",
"clpid": "Schramm-Stefan"
},
{
"family_name": "Stoecker",
"given_name": "Horst",
"clpid": "St\u00f6cker-Horst"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "In this work, we discuss the dense matter equation of state (EOS) for the extreme range of conditions encountered in neutron stars and their mergers. The calculation of the properties of such an EOS involves modeling different degrees of freedom (such as nuclei, nucleons, hyperons, and quarks), taking into account different symmetries, and including finite density and temperature effects in a thermodynamically consistent manner. We begin by addressing subnuclear matter consisting of nucleons and a small admixture of light nuclei in the context of the excluded volume approach. We then turn our attention to supranuclear homogeneous matter as described by the Chiral Mean Field (CMF) formalism. Finally, we present results from realistic neutron-star-merger simulations performed using the CMF model that predict signatures for deconfinement to quark matter in gravitational wave signals.",
"doi": "10.3390/universe5050129",
"issn": "2218-1997",
"publisher": "MDPI",
"publication": "Universe",
"publication_date": "2019-05",
"series_number": "5",
"volume": "5",
"issue": "5",
"pages": "Art. No. 129"
},
{
"id": "authors:t5sep-sk523",
"collection": "authors",
"collection_id": "t5sep-sk523",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297540000.57",
"type": "article",
"title": "Signatures of Quark-Hadron Phase Transitions in General-Relativistic Neutron-Star Mergers",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Dexheimer",
"given_name": "Veronica",
"orcid": "0000-0001-5578-2626",
"clpid": "Dexheimer-Veronica"
},
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Schramm",
"given_name": "Stefan",
"clpid": "Schramm-Stefan"
},
{
"family_name": "St\u00f6cker",
"given_name": "Horst",
"clpid": "St\u00f6cker-Horst"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "Merging binaries of neutron-stars are not only strong sources of gravitational waves, but also have the potential of revealing states of matter at densities and temperatures not accessible in laboratories. A crucial and long-standing question in this context is whether quarks are deconfined as a result of the dramatic increase in density and temperature following the merger. We present the first fully general-relativistic simulations of merging neutron-stars including quarks at finite temperatures that can be switched off consistently in the equation of state. Within our approach, we can determine clearly what signatures a quark-hadron phase transition would leave in the gravitational-wave signal. We show that if after the merger the conditions are met for a phase transition to take place at several times nuclear saturation density, they would lead to a postmerger signal considerably different from the one expected from the inspiral, that can only probe the hadronic part of the equations of state, and to an anticipated collapse of the merged object. We also show that the phase transition leads to a very hot and dense quark core that, when it collapses to a black hole, produces a ringdown signal different from the hadronic one. Finally, in analogy with what is done in heavy-ion collisions, we use the evolution of the temperature and density in the merger remnant to illustrate the properties of the phase transition in a QCD phase diagram.",
"doi": "10.1103/physrevlett.122.061101",
"issn": "0031-9007",
"publisher": "American Physical Society",
"publication": "Physical Review Letters",
"publication_date": "2019-02-15",
"series_number": "6",
"volume": "122",
"issue": "6",
"pages": "Art. No. 061101"
},
{
"id": "authors:3kh2r-czx06",
"collection": "authors",
"collection_id": "3kh2r-czx06",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230502-872813000.1",
"type": "article",
"title": "Neutron Star Mergers: Probing the EoS of Hot, Dense Matter by Gravitational Waves",
"author": [
{
"family_name": "Hanauske",
"given_name": "Matthias",
"orcid": "0000-0002-1060-1905",
"clpid": "Hanauske-Matthias"
},
{
"family_name": "Steinheimer",
"given_name": "Jan",
"orcid": "0000-0003-2565-7503",
"clpid": "Steinheimer-Jan"
},
{
"family_name": "Motornenko",
"given_name": "Anton",
"orcid": "0000-0003-3037-9923",
"clpid": "Motornenko-Anton"
},
{
"family_name": "Vovchenko",
"given_name": "Volodymyr",
"orcid": "0000-0002-2189-4766",
"clpid": "Vovchenko-Volodymyr"
},
{
"family_name": "Bovard",
"given_name": "Luke",
"orcid": "0000-0003-3555-062X",
"clpid": "Bovard-Luke"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Papenfort",
"given_name": "L. Jens",
"orcid": "0000-0002-6400-2553",
"clpid": "Papenfort-Ludwig-Jens"
},
{
"family_name": "Schramm",
"given_name": "Stefan",
"clpid": "Schramm-Stefan"
},
{
"family_name": "St\u00f6cker",
"given_name": "Horst",
"clpid": "St\u00f6cker-Horst"
}
],
"abstract": "Gravitational waves, electromagnetic radiation, and the emission of high energy particles probe the phase structure of the equation of state of dense matter produced at the crossroad of the closely related relativistic collisions of heavy ions and of binary neutron stars mergers. 3 + 1 dimensional special- and general relativistic hydrodynamic simulation studies reveal a unique window of opportunity to observe phase transitions in compressed baryon matter by laboratory based experiments and by astrophysical multimessenger observations. The astrophysical consequences of a hadron-quark phase transition in the interior of a compact star will be focused within this article. Especially with a future detection of the post-merger gravitational wave emission emanated from a binary neutron star merger event, it would be possible to explore the phase structure of quantum chromodynamics. The astrophysical observables of a hadron-quark phase transition in a single compact star system and binary hybrid star merger scenario will be summarized within this article. The FAIR facility at GSI Helmholtzzentrum allows one to study the universe in the laboratory, and several astrophysical signatures of the quark-gluon plasma have been found in relativistic collisions of heavy ions and will be explored in future experiments.",
"doi": "10.3390/particles2010004",
"issn": "2571-712X",
"publisher": "MDPI",
"publication": "Particles",
"publication_date": "2019-01",
"series_number": "1",
"volume": "2",
"issue": "1",
"pages": "44-56"
},
{
"id": "authors:r32dk-p8k15",
"collection": "authors",
"collection_id": "r32dk-p8k15",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297544000.58",
"type": "article",
"title": "Electromagnetic Emission from Blitzars and Its Impact on Non-repeating Fast Radio Bursts",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Nathanail",
"given_name": "Antonios",
"clpid": "Nathanail-Antonios"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "It has been suggested that a non-repeating fast radio burst (FRB) represents the final signal of a magnetized neutron star collapsing to a black hole. In this model, a supramassive neutron star supported by rapid rotation, will collapse to a black hole several thousand to million years after its birth, as a result of spin-down. The collapse violently snaps the magnetic field lines anchored on the stellar surface, thus producing an electromagnetic pulse that will propagate outward and accelerate electrons, thus producing a massive radio burst, i.e., a \"blitzar.\" We present a systematic study of the gravitational collapse of rotating and magnetized neutron stars, with special attention to far-field evolution at late times after the collapse. By considering a series of neutron stars with rotation ranging from zero to millisecond periods and different magnetic-field strengths, we show that the blitzar emission is very robust and always characterized by a series sub-millisecond pulses decaying exponentially in amplitude. The luminosity and energy released when the magnetosphere is destroyed are well-reproduced by a simple expression in terms of the stellar magnetic field and radius. Finally, we assess the occurrence of pair production during a blitzar scenario. We conclude that, for typical magnetic-field strengths of 10\u00b9\u00b2 G and spin frequencies of a few Hz, pair production is suppressed. Overall, the very good match between the results of the simulations and the luminosities normally observed for FRBs lends credibility to the blitzar model as a simple yet plausible explanation for the phenomenology of non-repeating FRBs.",
"doi": "10.3847/1538-4357/aad6ef",
"issn": "1538-4357",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2018-09-10",
"series_number": "2",
"volume": "864",
"issue": "2",
"pages": "Art. No. 117"
},
{
"id": "authors:c952s-xnr78",
"collection": "authors",
"collection_id": "c952s-xnr78",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297550000.59",
"type": "article",
"title": "New Constraints on Radii and Tidal Deformabilities of Neutron Stars from GW170817",
"author": [
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Weih",
"given_name": "Lukas R.",
"orcid": "0000-0002-9608-8689",
"clpid": "Weih-Lukas-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
},
{
"family_name": "Schaffner-Bielich",
"given_name": "J\u00fcrgen",
"orcid": "0000-0002-0079-6841",
"clpid": "Schaffner-Bielich-J\u00fcrgen"
}
],
"abstract": "We explore in a parameterized manner a very large range of physically plausible equations of state (EOSs) for compact stars for matter that is either purely hadronic or that exhibits a phase transition. In particular, we produce two classes of EOSs with and without phase transitions, each containing one million EOSs. We then impose constraints on the maximum mass (M < 2.16 M_\u2299) and on the dimensionless tidal deformability (\u039b\u0305 < 800) deduced from GW170817, together with recent suggestions of lower limits on \u039b\u0305. Exploiting more than 10\u2079 equilibrium models for each class of EOSs, we produce distribution functions of all the stellar properties and determine, among other quantities, the radius that is statistically most probable for any value of the stellar mass. In this way, we deduce that the radius of a purely hadronic neutron star with a representative mass of 1.4 M_\u2299 is constrained to be 12.00 < R_(1.4)/km < 13.45 at a 2\u03c3 confidence level, with a most likely value of R\u0305_(1.4) = 12.39 km; similarly, the smallest dimensionless tidal deformability is \u039b\u0305_(1.4 > 375, again at a 2\u03c3 level. On the other hand, because EOSs with a phase transition allow for very compact stars on the so-called \"twin-star\" branch, small radii are possible with such EOSs although not probable, i.e., 8.53 < R_(1.4)/km < 13.74 and R\u0305_(1.4) = 13.06 km at a 2\u03c3 level, with \u039b\u0305_(1.4) > 35.5 at a 3\u03c3 level. Finally, since these EOSs exhibit upper limits on \u039b\u0305, the detection of a binary with a total mass of 3.4 M_\u2299 and \u039b\u0305_(\n1.7) > 461 can rule out twin-star solutions.",
"doi": "10.1103/physrevlett.120.261103",
"issn": "0031-9007",
"publisher": "American Physical Society",
"publication": "Physical Review Letters",
"publication_date": "2018-06-29",
"series_number": "26",
"volume": "120",
"issue": "26",
"pages": "Art. No. 261103"
},
{
"id": "authors:tjp55-9yk38",
"collection": "authors",
"collection_id": "tjp55-9yk38",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297563000.61",
"type": "article",
"title": "Using Gravitational-wave Observations and Quasi-universal Relations to Constrain the Maximum Mass of Neutron Stars",
"author": [
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Weih",
"given_name": "Lukas R.",
"orcid": "0000-0002-9608-8689",
"clpid": "Weih-Lukas-R"
}
],
"abstract": "Combining the GW observations of merging systems of binary neutron stars and quasi-universal relations, we set constraints on the maximum mass that can be attained by nonrotating stellar models of neutron stars. More specifically, exploiting the recent observation of the GW event GW170817 and drawing from basic arguments on kilonova modeling of GRB 170817A together with the quasi-universal relation between the maximum mass of nonrotating stellar models M_(TOV) and the maximum mass supported through uniform rotation M_(max) = (1.20_(-0.05)^(+0.02)) M_(TOV), we set limits for the maximum mass to be 2.01_(-0.04)^(+0.04) \u2a7d M(TOV)/M_\u2299 \u227e 2.16_(-0.15)^(+0.17), where the lower limit in this range comes from pulsar observations. Our estimate, which follows a very simple line of arguments and does not rely on the modeling of the electromagnetic signal in terms of numerical simulations, can be further refined as new detections become available. We briefly discuss the impact that our conclusions have on the equation of state of nuclear matter.",
"doi": "10.3847/2041-8213/aaa401",
"issn": "2041-8213",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2018-01-10",
"series_number": "2",
"volume": "852",
"issue": "2",
"pages": "Art. No. L25"
},
{
"id": "authors:ty81g-vge09",
"collection": "authors",
"collection_id": "ty81g-vge09",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297567000.62",
"type": "article",
"title": "On the stability and maximum mass of differentially rotating relativistic stars",
"author": [
{
"family_name": "Weih",
"given_name": "Lukas R.",
"orcid": "0000-0002-9608-8689",
"clpid": "Weih-Lukas-R"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "The stability properties of rotating relativistic stars against prompt gravitational collapse to a black hole are rather well understood for uniformly rotating models. This is not the case for differentially rotating neutron stars, which are expected to be produced in catastrophic events such as the merger of binary system of neutron stars or the collapse of a massive stellar core. We consider sequences of differentially rotating equilibrium models using the j-constant law and by combining them with their dynamical evolution, we show that a sufficient stability criterion for differentially rotating neutron stars exists similar to the one of their uniformly rotating counterparts. Namely: along a sequence of constant angular momentum, a dynamical instability sets in for central rest-mass densities slightly below the one of the equilibrium solution at the turning point. In addition, following Breu & Rezzolla, we show that 'quasi-universal' relations can be found when calculating the turning-point mass. In turn, this allows us to compute the maximum mass allowed by differential rotation, M_(max,dr), in terms of the maximum mass of the non-rotating configuration, M_(TOV)\u2060, finding that M_(max,dr) \u2243 (1.54 \u00b1 0.05)M_(TOV) for all the equations of state we have considered.",
"doi": "10.1093/mnrasl/slx178",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2018-01",
"series_number": "1",
"volume": "473",
"issue": "1",
"pages": "L126-L130"
},
{
"id": "authors:3vrpq-5qt74",
"collection": "authors",
"collection_id": "3vrpq-5qt74",
"cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230501-297574000.63",
"type": "article",
"title": "Gravitational collapse to a Kerr\u2013Newman black hole",
"author": [
{
"family_name": "Nathanail",
"given_name": "Antonios",
"clpid": "Nathanail-Antonios"
},
{
"family_name": "Most",
"given_name": "Elias R.",
"orcid": "0000-0002-0491-1210",
"clpid": "Most-E-R"
},
{
"family_name": "Rezzolla",
"given_name": "Luciano",
"orcid": "0000-0002-1330-7103",
"clpid": "Rezzolla-Luciano"
}
],
"abstract": "We present the first systematic study of the gravitational collapse of rotating and magnetized neutron stars to charged and rotating (Kerr\u2013Newman) black holes. In particular, we consider the collapse of magnetized and rotating neutron stars assuming that no pair-creation takes place and that the charge density in the magnetosphere is so low that the stellar exterior can be described as an electrovacuum. Under these assumptions, which are rather reasonable for a pulsar that has crossed the 'death line', we show that when the star is rotating, it acquires a net initial electrical charge, which is then trapped inside the apparent horizon of the newly formed back hole. We analyse a number of different quantities to validate that the black hole produced is indeed a Kerr\u2013Newman one and show that, in the absence of rotation or magnetic field, the end result of the collapse is a Schwarzschild or Kerr black hole, respectively.",
"doi": "10.1093/mnrasl/slx035",
"issn": "1745-3925",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society: Letters",
"publication_date": "2017-07",
"series_number": "1",
"volume": "469",
"issue": "1",
"pages": "L31-L35"
}
]