[
{
"id": "authors:xf8hr-5bk43",
"collection": "authors",
"collection_id": "xf8hr-5bk43",
"cite_using_url": "https://authors.library.caltech.edu/records/xf8hr-5bk43",
"type": "article",
"title": "Quantitative Spectroscopic Diagnostics for FU Orionis-type Young Stellar Objects",
"author": [
{
"family_name": "Portnoi",
"given_name": "Evan R.",
"clpid": "Portnoi-Evan-R"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
}
],
"abstract": "We present near-infrared spectroscopic diagnostics that can be used to identify FU Orionis stars (FUOrs). These young stellar objects are currently in a state of extreme outburst, caused by enhanced mass inflow from their accretion disks. The disks give FUOrs a distinct multi-temperature optical and infrared spectrum. Considering both the predicted spectrum from a disk atmosphere model and existing spectral diagnostics from the literature, we identify key atomic and molecular features for characterizing FUOrs. Some of the chosen features are proxies for temperature, others are sensitive to surface gravity, and still others probe disk winds. Using the Palomar Observatory/Hale Telescope and TripleSpec spectrograph, we gathered near-infrared spectra of 28 known FUOrs. We use standard equivalent widths to determine the strength of atomic lines, and we design several band ratios for measuring molecular features. We compare the measurements between our spectra and a control sample of late-type dwarfs and evolved stars from the Infrared Telescope Facility Spectral Library. By considering the relative distributions of these samples in our defined spectral diagnostics, we propose a number of parameter spaces that can distinguish FUOr disks from normal stars. The rate of discovery of FUOr candidates has increased significantly in recent years, largely due to the increasing prevalence of time-domain surveys. Our proposed diagnostics will allow new photometric candidates to be confirmed or refuted as such.
",
"doi": "10.3847/1538-4357/ae6dbc",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-07-01",
"series_number": "1",
"volume": "1005",
"issue": "1",
"pages": "57"
},
{
"id": "authors:m433h-dnd90",
"collection": "authors",
"collection_id": "m433h-dnd90",
"cite_using_url": "https://authors.library.caltech.edu/records/m433h-dnd90",
"type": "article",
"title": "The FUor Mass Distribution Matches the Solar Neighborhood Initial Mass Function: Evidence for a Universal Eruptive Phase",
"author": [
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
}
],
"abstract": "\n
Eruptive accretion events are expected to play an important role in the mass-buildup stage of individual star formation. FU Ori objects (FUors) experience the most extreme eruptive outbursts, which raise the accretion rate of the disk from 10−9–10−8 to 10−5–10−4 M\u2299 yr−1 and last for decades. During an outburst, the disk is approximately 100 times brighter than the star, making direct study of the central star impossible. However, the disk is expected to be in Keplerian rotation around the star, enabling indirect constraints on properties of the central source via observations of the disk. Using 1–2.4 μm high-resolution spectra of several tens of FUors, we demonstrate the expected Keplerian rotation in their inner disks. We then adopt a Keplerian rotational-broadening profile to model the line profiles of spectral lines and, focusing on the H-band region, we infer the mass distribution of FUors. We finally show that this mass distribution is consistent with inferred solar neighborhood initial mass functions, suggesting all young stars undergo a period of FUor outbursts in their pre-main-sequence evolution.
\n
Magnetic fields play a central role in the evolution of pre-main-sequence (PMS) stars, yet direct observational constraints on their variability over rotational and multiyear timescales remain scarce. We investigate the temporal behavior of surface magnetic fields in a sample of nine PMS stars observed with the Immersion GRating INfrared Spectrometer (IGRINS), using 489 high-resolution near-infrared spectra drawn from the Raw and Reduced IGRINS Spectral Archive (or RRISA). We fit each epoch with magnetic synthetic spectra to derive the mean surface magnetic field strength \u3008 Bf \u3009 and detect correlated magnetic and thermal variability in six of the nine stars while being able to recover the known stellar rotation period in at least one observing season for all six. We find that not only the mean magnetic field strength and effective temperature evolve on year-long baselines, but so does the amplitude of the rotational modulation signal (which in some cases weakens or disappears entirely). This behavior indicates that magnetic variability is driven by both changes in the total magnetic flux and the spatial distribution and contrast of surface magnetic inhomogeneities. For two stars in the sample with starspot measurements, we find that the magnetic filling factors are systematically larger than those inferred from temperature variations, implying that magnetic regions extend beyond the coolest spotted areas and occupy a broader fraction of the stellar surface (i.e., plages). These results provide direct evidence that PMS magnetic variability is structured, rotationally modulated, and evolves on multiyear timescales.
",
"doi": "10.3847/1538-4357/ae7a64",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-07-01",
"series_number": "1",
"volume": "1005",
"issue": "1",
"pages": "121"
},
{
"id": "authors:gw1yv-4at02",
"collection": "authors",
"collection_id": "gw1yv-4at02",
"cite_using_url": "https://authors.library.caltech.edu/records/gw1yv-4at02",
"type": "article",
"title": "A Parameterized YSO Accretion Disk Model with Increasing Accretion Rate: Predicted Outburst Lightcurves",
"author": [
{
"family_name": "Das",
"given_name": "Gautam",
"orcid": "0009-0001-0200-2574",
"clpid": "Das-Gautam"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
}
],
"abstract": "A subclass among young stellar objects, known as FU Ori type stars, undergo sudden rises in luminosity by several orders of magnitude on timescales of a few months to a few years, and decay back to quiescence on timescales of a few decades. Modelling the lightcurves of these objects is crucial to understanding how different components of these accretion disk systems evolve during outburst. For this purpose, we use a parametric model that couples the stellar photospheric emission, magnetospheric accretion shocks, an irradiated dust disk, and a viscously heated gas disk. We adopt time-dependent accretion rate profiles that mimic the observed morphologies of FU Ori outburst lightcurves, and we use the accretion model infrastructure to simulate multiband lightcurves, as well as color curves. The model enables us to study how different components dominate the flux in each band over the course of an outburst, providing insight into star–magnetosphere–disk interactions throughout the outburst cycle. We find that throughout an accretion outburst, red optical and near-infrared lightcurves generally follow the same or very similar form as the input accretion profile, being sensitive to heating in the accretion shocks and inner gas disk, while mid-infrared lightcurves are more responsive to the location and heating of the innermost dust disk.
",
"doi": "10.3847/1538-4357/ae6e3b",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-06-20",
"series_number": "2",
"volume": "1004",
"issue": "2",
"pages": "201"
},
{
"id": "authors:6zq6m-a0w28",
"collection": "authors",
"collection_id": "6zq6m-a0w28",
"cite_using_url": "https://authors.library.caltech.edu/records/6zq6m-a0w28",
"type": "article",
"title": "The circumstellar environment of the young, low-mass dipper star JH 223. Accretion and large-scale magnetic field topology",
"author": [
{
"family_name": "Freitas",
"given_name": "T. P.",
"orcid": "0009-0008-9261-7396"
},
{
"family_name": "Bouvier",
"given_name": "J.",
"orcid": "0000-0002-7450-6712"
},
{
"family_name": "Zaire",
"given_name": "B.",
"orcid": "0000-0002-9328-9530"
},
{
"family_name": "Alencar",
"given_name": "S. H. P.",
"orcid": "0000-0002-5171-8376"
},
{
"family_name": "Sousa",
"given_name": "A. P.",
"orcid": "0000-0001-7397-8972"
},
{
"family_name": "Rebull",
"given_name": "L.",
"orcid": "0000-0001-6381-515X",
"clpid": "Rebull-Luisa-M"
},
{
"family_name": "Bayo",
"given_name": "A.",
"orcid": "0000-0001-7868-7031"
},
{
"family_name": "Frasca",
"given_name": "A.",
"orcid": "0000-0002-0474-0896"
},
{
"family_name": "Alonso-Santiago",
"given_name": "J.",
"orcid": "0000-0001-9707-3107"
},
{
"family_name": "Grankin",
"given_name": "K.",
"orcid": "0000-0001-5707-8448"
},
{
"family_name": "Contreras Pe\u00f1a",
"given_name": "C.",
"orcid": "0000-0003-1894-1880"
},
{
"family_name": "Cody",
"given_name": "A. M.",
"orcid": "0000-0002-3656-6706"
},
{
"family_name": "Hillenbrand",
"given_name": "L. A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Carmona",
"given_name": "A.",
"orcid": "0000-0003-2471-1299"
}
],
"abstract": "Context. Studies of magnetospheric accretion and magnetic field topology in T Tauri stars have advanced over the years, but their applications to fully convective, very-low-mass T Tauri stars remain relatively unexplored.
\nAims. We aim to analyze the circumstellar environment of the very-low-mass dipper-like star JH 223 by investigating the accretion process and characterizing its large-scale magnetic field topology.
\nMethods. We analyzed the photometric variability of JH 223 using observations from multiple telescopes, including K2, TESS, and LCOGT across different epochs. Additionally, we used Gemini/GRACES spectroscopic and CFHT/SPIRou spectropolarimetric data to investigate the star-disk interaction and to characterize the large-scale stellar magnetic field using Zeeman-Doppler imaging.
\nResults. JH 223 is a fully convective classical T Tauri star with an age of about 3 Myr and a mass of 0.4 M\u2299. The large-scale surface magnetic field is predominantly poloidal, with a 250 G dipolar component. The dipole field strength and the mass accretion rate indicate that the disk gas truncation radius is located near the corotation radius (6\u2005±\u20051 R\u2605). The star-disk interaction, combined with the inclined dipole, generates accretion columns that warp the inner disk. As the star rotates, this warp periodically obscures the stellar surface every 3.31 days, producing the dipper light curves. The same period is also detected in variations of the radial velocity and the longitudinal magnetic field. The accretion columns, traced by strong redshifted absorption components in Hα and He I 1083nm, are associated with the inner disk warp, as they occur around the same rotational phase. The accretion process in JH 223 is dynamic, transitioning from an unstable to a stable regime over a few weeks, consistent with predictions from magnetohydrodynamic simulations of the star-disk interaction.
\nConclusions. Results from multi-technique observations suggest that the magnetospheric accretion model remains valid for fully convective very-low-mass young stars.
",
"doi": "10.1051/0004-6361/202558514",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2026-05",
"volume": "709",
"pages": "A243"
},
{
"id": "authors:jnk4v-84q13",
"collection": "authors",
"collection_id": "jnk4v-84q13",
"cite_using_url": "https://authors.library.caltech.edu/records/jnk4v-84q13",
"type": "article",
"title": "SPHEREx as a Frontier for Infrared Transients: Classification of New Galactic FU Ori Outbursts and Classical Novae",
"author": [
{
"family_name": "Karambelkar",
"given_name": "Viraj R.",
"orcid": "0000-0003-2758-159X"
},
{
"family_name": "De",
"given_name": "Kishalay",
"orcid": "0000-0002-8989-0542"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Sokoloski",
"given_name": "J. L."
},
{
"family_name": "Frostig",
"given_name": "Danielle",
"orcid": "0000-0002-7197-9004"
},
{
"family_name": "Dalcanton",
"given_name": "Julianne",
"orcid": "0000-0002-1264-2006"
}
],
"abstract": "\n
We demonstrate proof of concept of a new strategy for studying infrared (IR) transients enabled by the newly launched SPHEREx space mission, by leveraging its synergy with the NEOWISE space mission. With its 15 yr baseline and all-sky mid-IR coverage, NEOWISE provides an excellent avenue to discover thousands of slowly evolving IR outbursts. With its all-sky spectrophotometric coverage and mid-IR sensitivity matching NEOWISE, SPHEREx is uniquely positioned to provide low-resolution IR spectra for the vast majority of these outbursts, several of which are too obscured for ground-based spectroscopic classification. As a demonstration of this approach, we present SPHEREx spectra for eight Galactic transients identified in NEOWISE. This sample includes two previously known FU Orionis-type (FUOr) outbursts whose SPHEREx spectra exhibit clear signatures of cool molecular absorption and three known classical novae showing strong emission lines in SPHEREx. Using these sources as templates, we identify two new FUOrs and one previously missed Galactic nova. Our results highlight the potential of SPHEREx for systematic explorations of the relatively underexplored dynamic IR sky.
\n
\n
We present revised stellar ages for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius (Upper Sco) star-forming region, derived using stellar dynamical masses to constrain isochronal ages from five PMS stellar evolutionary models. We find that mass-constrained stellar ages for all model sets are more consistent with the older, ∼8–11 Myr age for Upper Sco derived using earlier-type stars. Additionally, applying the independent mass constraint to isochronal ages tends to (1) increase stellar ages for most model sets, and (2) decrease age scatter for individual sources between model sets. Models that account for global magnetic fields consistently provide the best match to our observations: they change comparatively little when the mass constraint is applied, and produce 9–10 Myr ages under both unconstrained and mass-constrained conditions. Most standard (nonmagnetic) models produce younger ages (3–5 Myr) when unconstrained, but older ages (6–9 Myr) when constrained by dynamical mass. Our results are consistent with recent literature findings that suggest median disk lifetimes may be \u22732× longer than previously thought.
\n
Episodic mass accretion is the dominant mechanism for mass assembly in the protostellar phase. Although prior optical time-domain searches have allowed detailed studies of individual outbursts, these searches remain insensitive to the earliest stages of star formation. In this paper, we present the characterization of two FU Orionis (FUor) outbursts identified using the combination of the ground-based, near-infrared Wide-field Infrared Transient Explorer (WINTER) and the space-based, mid-infrared NEOWISE survey. Supplemented with near-infrared spectroscopic follow-up, we show that both objects are bona fide FUor type outbursts based on (i) their proximity to star-forming regions, (ii) large amplitude (2–4 magnitudes) infrared brightening over the last decade, (iii) progenitor colors consistent with embedded (Class I) protostars, and (iv) \"mixed-temperature\" infrared spectra exhibiting characteristic signatures of cool outer envelopes and a hot inner disk with a wind. While one source, WNTR24-cua, is a known FUor that we independently recover; the second source, WNTR24-egv, is a newly confirmed object. Neither source is detected in contemporaneous ground-based optical imaging, despite flux limits \u2273100× fainter than their infrared brightness, demonstrating the capabilities of WINTER to identify heavily obscured young stellar object outbursts. We highlight the capabilities of the Galactic Plane Survey of the recently commissioned WINTER observatory in addressing the poorly understood FUor population with its unique combination of real-time detection capabilities, multicolor sensitivity, weekly cadence, and wide area coverage.
",
"doi": "10.3847/1538-4357/ae2322",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2026-02-01",
"series_number": "2",
"volume": "997",
"issue": "2",
"pages": "263"
},
{
"id": "authors:5qtdn-t6t93",
"collection": "authors",
"collection_id": "5qtdn-t6t93",
"cite_using_url": "https://authors.library.caltech.edu/records/5qtdn-t6t93",
"type": "article",
"title": "A young progenitor for the most common planetary systems in the Galaxy",
"author": [
{
"family_name": "Livingston",
"given_name": "John H.",
"orcid": "0000-0002-4881-3620"
},
{
"family_name": "Petigura",
"given_name": "Erik A.",
"orcid": "0000-0003-0967-2893"
},
{
"family_name": "David",
"given_name": "Trevor J."
},
{
"family_name": "Masuda",
"given_name": "Kento"
},
{
"family_name": "Owen",
"given_name": "James",
"orcid": "0000-0002-4856-7837"
},
{
"family_name": "Nesvorn\u00fd",
"given_name": "David",
"orcid": "0000-0002-4547-4301"
},
{
"family_name": "Batygin",
"given_name": "Konstantin",
"orcid": "0000-0002-7094-7908",
"clpid": "Batygin-K"
},
{
"family_name": "de Leon",
"given_name": "Jerome"
},
{
"family_name": "Mori",
"given_name": "Mayuko",
"orcid": "0000-0003-1368-6593"
},
{
"family_name": "Ikuta",
"given_name": "Kai"
},
{
"family_name": "Fukui",
"given_name": "Akihiko",
"orcid": "0000-0002-4909-5763"
},
{
"family_name": "Watanabe",
"given_name": "Noriharu"
},
{
"family_name": "Orell Miquel",
"given_name": "Jaume",
"orcid": "0000-0003-2066-8959"
},
{
"family_name": "Murgas",
"given_name": "Felipe",
"orcid": "0000-0001-9087-1245"
},
{
"family_name": "Parviainen",
"given_name": "Hannu",
"orcid": "0000-0001-5519-1391"
},
{
"family_name": "Korth",
"given_name": "Judith",
"orcid": "0000-0002-0076-6239"
},
{
"family_name": "Libotte",
"given_name": "Florence"
},
{
"family_name": "Abreu Garc\u00eda",
"given_name": "N\u00e9stor",
"orcid": "0009-0002-5067-5463"
},
{
"family_name": "Gallardo",
"given_name": "Pedro Pablo Meni",
"orcid": "0009-0001-7943-0075"
},
{
"family_name": "Narita",
"given_name": "Norio",
"orcid": "0000-0001-8511-2981"
},
{
"family_name": "Pall\u00e9",
"given_name": "Enric",
"orcid": "0000-0003-0987-1593"
},
{
"family_name": "Tamura",
"given_name": "Motohide",
"orcid": "0000-0002-6510-0681"
},
{
"family_name": "Yonehara",
"given_name": "Atsunori"
},
{
"family_name": "Ridden-Harper",
"given_name": "Andrew"
},
{
"family_name": "Bieryla",
"given_name": "Allyson",
"orcid": "0000-0001-6637-5401"
},
{
"family_name": "Trani",
"given_name": "Alessandro A."
},
{
"family_name": "Mamajek",
"given_name": "Eric E.",
"orcid": "0000-0003-2008-1488",
"clpid": "Mamajek-Eric-E"
},
{
"family_name": "Ciardi",
"given_name": "David R.",
"orcid": "0000-0002-5741-3047",
"clpid": "Ciardi-David-R"
},
{
"family_name": "Gorjian",
"given_name": "Varoujan",
"orcid": "0000-0002-8990-2101",
"clpid": "Gorjian-Varoujan"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Rebull",
"given_name": "Luisa M.",
"orcid": "0000-0001-6381-515X",
"clpid": "Rebull-Luisa-M"
},
{
"family_name": "Newton",
"given_name": "Elisabeth R."
},
{
"family_name": "Mann",
"given_name": "Andrew W.",
"orcid": "0000-0003-3654-1602"
},
{
"family_name": "Vanderburg",
"given_name": "Andrew",
"orcid": "0000-0001-7246-5438"
},
{
"family_name": "Stef\u00e1nsson",
"given_name": "Gu\u00f0mundur"
},
{
"family_name": "Mahadevan",
"given_name": "Suvrath",
"orcid": "0000-0001-9596-7983"
},
{
"family_name": "Ca\u00f1as",
"given_name": "Caleb"
},
{
"family_name": "Ninan",
"given_name": "Joe"
},
{
"family_name": "Higuera",
"given_name": "Jesus",
"orcid": "0000-0002-3985-8528"
},
{
"family_name": "Todorov",
"given_name": "Kamen",
"orcid": "0000-0002-9276-8118"
},
{
"family_name": "D\u00e9sert",
"given_name": "Jean-Michel",
"orcid": "0000-0002-0875-8401"
},
{
"family_name": "Pino",
"given_name": "Lorenzo",
"orcid": "0000-0002-1321-8856"
}
],
"abstract": "The Galaxy's most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order of magnitude. The young star V1298 Tau hosts one such compact planetary system, albeit with four planets that are uncommonly large (5 to 10 Earth radii). The planets form a chain of near-resonances that result in transit-timing variations of several hours. Here we present a multi-year campaign to characterize this system with transit-timing variations, a method insensitive to the intense magnetic activity of the star. Through targeted observations, we first resolved the previously unknown orbital period of the outermost planet. The full 9-year baseline from these and archival data then enabled robust determination of the masses and orbital parameters for all four planets. We find the planets have low, sub-Neptune masses and nearly circular orbits, implying a dynamically tranquil history. Their low masses and large radii indicate that the inner planets underwent a period of rapid cooling immediately after dispersal of the protoplanetary disk. Still, they are much less dense than mature planets of comparable size. We predict the planets will contract to 1.5–4.0 Earth radii and join the population of super-Earths and sub-Neptunes that nature produces in abundance.
",
"doi": "10.1038/s41586-025-09840-z",
"pmcid": "PMC12779570",
"issn": "0028-0836",
"publisher": "Nature Publishing Group",
"publication": "Nature",
"publication_date": "2026-01-08",
"series_number": "8096",
"volume": "649",
"issue": "8096",
"pages": "310-314"
},
{
"id": "authors:4hxey-rjx12",
"collection": "authors",
"collection_id": "4hxey-rjx12",
"cite_using_url": "https://authors.library.caltech.edu/records/4hxey-rjx12",
"type": "article",
"title": "Ultraviolet science and instrumentation: on the way to the NASA Habitable Worlds Observatory and beyond\u2014workshop highlights",
"author": [
{
"family_name": "Nikzad",
"given_name": "Shouleh",
"orcid": "0009-0004-1255-1018",
"clpid": "Nikzad-S"
},
{
"family_name": "Kurczynski",
"given_name": "Peter",
"orcid": "0000-0002-8816-5146"
},
{
"family_name": "Youngblood",
"given_name": "Allison",
"orcid": "0000-0002-1176-3391"
},
{
"family_name": "Shkolnik",
"given_name": "Evgenya",
"orcid": "0000-0002-7260-5821"
},
{
"family_name": "Mennesson",
"given_name": "Bertrand",
"orcid": "0000-0003-4205-4800",
"clpid": "Mennesson-Bertrand"
},
{
"family_name": "Hosseini",
"given_name": "Sona",
"orcid": "0009-0004-7045-5825",
"clpid": "Hosseini-Sona"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Hamden",
"given_name": "Erika",
"orcid": "0000-0002-3131-7372"
},
{
"family_name": "Beaton",
"given_name": "Rachael"
},
{
"family_name": "Alavi",
"given_name": "Anahita",
"orcid": "0000-0002-8630-6435",
"clpid": "Alavi-Anahita"
},
{
"family_name": "France",
"given_name": "Kevin",
"orcid": "0000-0002-1002-3674"
},
{
"family_name": "Stierwalt",
"given_name": "Sabrina",
"orcid": "0000-0002-7532-3328"
},
{
"family_name": "Scowen",
"given_name": "Paul",
"orcid": "0000-0002-9071-6744"
},
{
"family_name": "Moustakas",
"given_name": "Leonidas",
"orcid": "0000-0003-3030-2360",
"clpid": "Moustakas-Leonidas"
},
{
"family_name": "Beichman",
"given_name": "Charles",
"orcid": "0000-0002-5627-5471",
"clpid": "Beichman-C-A"
},
{
"family_name": "Ardila",
"given_name": "David",
"orcid": "0000-0002-2564-8116",
"clpid": "Ardila-David"
}
],
"abstract": "We summarize a 3-day workshop held on May 7–9, 2024, at NASA's Jet Propulsion Laboratory in Pasadena, CA, focused on exploring science opportunities through ultraviolet (UV) observations and the required instrumentation and technology for various platforms, ranging from CubeSats to flagship missions. The workshop supports the research community's efforts as it prepares for the Habitable Worlds Observatory (HWO) and preceding UV mission opportunities that may be enabling of HWO. UV light is endowed with rich spectroscopic information that can inform many aspects of astrophysics, including the characterization of interstellar medium components, stellar atmospheres, transients of all types, and exoplanet atmospheres, to name just a few. The workshop featured invited and contributed presentations, panel discussions, and poster sessions. Participants discussed science priorities and possibilities through space-based UV observations, explored the necessary instrumentation for these measurements, and identified both existing and needed technologies.
",
"doi": "10.1117/1.jatis.11.4.042232",
"issn": "2329-4124",
"publisher": "SPIE-Intl Soc Optical Eng",
"publication": "Journal of Astronomical Telescopes, Instruments, and Systems",
"publication_date": "2025-12-22",
"series_number": "04",
"volume": "11",
"issue": "04"
},
{
"id": "authors:g4097-hx049",
"collection": "authors",
"collection_id": "g4097-hx049",
"cite_using_url": "https://authors.library.caltech.edu/records/g4097-hx049",
"type": "article",
"title": "The Optical Photometric Variability of Herbig Ae/Be Stars from TESS",
"author": [
{
"family_name": "Cody",
"given_name": "Ann Marie",
"orcid": "0000-0002-3656-6706"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Chandragiri",
"given_name": "Shreya"
},
{
"family_name": "Morgan",
"given_name": "Marvin",
"orcid": "0000-0003-4022-6234"
}
],
"abstract": "We have carried out a photometric time domain study of 188 intermediate-mass young stars observed in Full Frame Image mode with the Transiting Exoplanet Survey Satellite (TESS) satellite over the first 3.3 yr of its mission. The majority of these targets are classified as Herbig Ae/Be stars (HAeBes). All were monitored at optical wavelengths for at least one 27 day TESS sector, with many having multiple sectors of data. From a custom aperture photometry pipeline, we produced light curves and analyzed the variability therein, as a function of stellar and circumstellar properties. Based on visual and statistical analysis, we find that ∼95% of HAeBes are variable on timescales of 10 minutes to one month, with the most common light-curve morphology being stochastic. Approximately 15% of the set display quasiperiodic variability. In comparison to sets of low-mass T Tauri stars monitored with optical space telescopes, the Herbig Ae/Be stars display a much lower incidence of \"dipper\" behaviors (quasiperiodic or aperiodic fading events), as well as periodic modulations. As posited by previous work, we conclude that magnetic starspots are rare on HAeBes, and that the inner circumstellar dust rims of these objects lie at substantially larger radii than for low-mass young stars. Beyond these differences, the accretion dynamics of young stars less than ∼7 M\u2299 appear to be largely consistent based on their time domain properties from data streams of up to three months' duration. We do, however, find tentative evidence for a change in variability amplitude above this mass boundary, particularly for quasiperiodic behavior.
",
"doi": "10.3847/1538-4357/ae119a",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-12-01",
"series_number": "2",
"volume": "994",
"issue": "2",
"pages": "253"
},
{
"id": "authors:kzsp4-e5k59",
"collection": "authors",
"collection_id": "kzsp4-e5k59",
"cite_using_url": "https://authors.library.caltech.edu/records/kzsp4-e5k59",
"type": "article",
"title": "Dynamical Masses for 23 Pre-main-sequence Stars in Upper Scorpius: A Critical Test of Stellar Evolutionary Models",
"author": [
{
"family_name": "Towner",
"given_name": "A. P. M.",
"orcid": "0000-0001-5933-824X"
},
{
"family_name": "Eisner",
"given_name": "J. A.",
"orcid": "0000-0002-1031-4199"
},
{
"family_name": "Sheehan",
"given_name": "P. D.",
"orcid": "0000-0002-9209-8708"
},
{
"family_name": "Hillenbrand",
"given_name": "L. A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Wu",
"given_name": "Y.-L.",
"orcid": "0000-0002-4392-1446"
}
],
"abstract": "We present dynamical masses for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius star-forming region. These masses were derived from the Keplerian rotation of CO disk gas using the Markov Chain Monte Carlo radiative-transfer package pdspy and a flared-disk model with 15 free parameters. We compare our dynamical masses to those derived from five PMS evolutionary models, and find that most models consistently underestimate stellar mass by \u227325%. Models with updated treatment of stellar magnetic fields are a notable exception—they consistently return stellar masses in good agreement with the dynamical results. We find that the magnetic models’ performance is valid even at low masses, in contrast with some literature results suggesting they may overestimate stellar mass for M\u22c6 \u2272 0.6 M\u2299. Our results are consistent with dynamical versus isochronal evaluations for younger samples (e.g., Taurus, 1–3 Myr), and extend the systematic evaluation of stellar evolutionary models up to stars ∼11 Myr in age. Finally, we derive disk dust masses to evaluate whether using dynamical masses versus isochronal masses changes the slope of the log(Mdust)−log(M\u22c6) relation. We derive a slightly shallower relation using dynamical masses versus isochronal masses, but the slopes of these relations agree within uncertainties. In all cases, we derive a steeper than linear relation for log(Mdust)−log(M\u22c6), consistent with previous literature results for Upper Sco.
",
"doi": "10.3847/1538-4357/ae0f18",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-12-01",
"series_number": "2",
"volume": "994",
"issue": "2",
"pages": "214"
},
{
"id": "authors:x86cr-knc32",
"collection": "authors",
"collection_id": "x86cr-knc32",
"cite_using_url": "https://authors.library.caltech.edu/records/x86cr-knc32",
"type": "article",
"title": "The Near-ultraviolet Spectra of FU Orionis Accretion Disks",
"author": [
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Herczeg",
"given_name": "Gregory J.",
"orcid": "0000-0002-7154-6065"
},
{
"family_name": "France",
"given_name": "Kevin",
"orcid": "0000-0002-1002-3674"
}
],
"abstract": "We present the results of the first high-sensitivity near-ultraviolet (NUV; 1800–3200 Å) survey of FU Ori objects, using the Hubble Space Telescope STIS spectrograph. We compare new low-resolution spectra for six sources with predictions from accretion disk models and find that all show emission in excess of the disk model spectrum. The physical properties of the NUV emission excess are very consistent among the sample, with a mean luminosity of 10−1.11±0.4 L\u2299 and temperature of 16,400 ± 2600 K—despite spanning 0.9 dex in M*, 1.3 dex in M, and 0.7 dex in Lacc. We use the spectra to conclusively rule out the existence of a hot boundary layer in FU Ori accretion disks. We then discuss the source of the excess emission in the context of recent simulations of FU Ori outbursts and boundary layer accretion. The UV spectra also show the often-seen C ii] 2326 Å multiplet and Mg ii 2796/2803 Å doublet, as well as the unusual Fe ii] 2507/2509 Å doublet, a feature that is not seen in the existing UV spectra of other young stellar objects. We measure and compare the luminosities of these lines in outbursting with those in nonoutbursting objects.
",
"doi": "10.3847/2041-8213/ae1830",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2025-11-20",
"series_number": "1",
"volume": "994",
"issue": "1",
"pages": "L12"
},
{
"id": "authors:dtaek-ts226",
"collection": "authors",
"collection_id": "dtaek-ts226",
"cite_using_url": "https://authors.library.caltech.edu/records/dtaek-ts226",
"type": "article",
"title": "The Hot Inner AU of V883 Ori",
"author": [
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "K\u00f3sp\u00e1l",
"given_name": "\u00c1gnes",
"orcid": "0000-0001-7157-6275"
}
],
"abstract": "The V883 Ori system is a rapidly accreting young stellar object that has been used as a laboratory for studying the molecular inventory of young circumstellar disks with high luminosity. We simultaneously fit high-resolution spectroscopy and medium-resolution spectrophotometry of the system to constrain the physical conditions in the inner au. Using our thin viscous accretion disk model, we find M \u0307 = 10^(−3.9±0.2) M\u2299 yr−1, Rinner = 5.86 ± 1 R\u2299, i = 38:2 ± 3°, and AV = 20.8 ± 0.7 mag, resulting in an accretion luminosity of 458 L\u2299 and maximum disk temperature of 7045 K. The optical portion of the spectral energy distribution greatly exceeds the flux level expected for a highly extincted accretion disk. We propose that the excess emission arises from a contribution due to scattering of the accretion disk spectrum off nearby envelope material that is viewed along a line of sight with less extinction. Additionally, we use photometric observations spanning 137 years to demonstrate that the source has accreted at least 18 MJup of disk material to date. Finally, we discuss the importance of considering both the viscous heating from the midplane and the consequent irradiation effects on the outer disk when modeling the temperature structure to reproduce millimeter-wavelength observations.
",
"doi": "10.3847/1538-4357/ae0646",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-11-01",
"series_number": "1",
"volume": "993",
"issue": "1",
"pages": "38"
},
{
"id": "authors:ta9kb-qge12",
"collection": "authors",
"collection_id": "ta9kb-qge12",
"cite_using_url": "https://authors.library.caltech.edu/records/ta9kb-qge12",
"type": "article",
"title": "A Spectral Library and Census of Near-infrared Stellar Large-amplitude Variables from Palomar Gattini-IR",
"author": [
{
"family_name": "Earley",
"given_name": "Nicholas",
"orcid": "0000-0001-6627-9903",
"clpid": "Earley-Nicholas"
},
{
"family_name": "Karambelkar",
"given_name": "Viraj",
"orcid": "0000-0003-2758-159X"
},
{
"family_name": "Kasliwal",
"given_name": "Mansi",
"orcid": "0000-0002-5619-4938",
"clpid": "Kasliwal-M-M"
},
{
"family_name": "De",
"given_name": "Kishalay",
"orcid": "0000-0002-8989-0542"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Soria",
"given_name": "Roberto",
"orcid": "0000-0002-4622-796X"
},
{
"family_name": "Suresh",
"given_name": "Aswin",
"orcid": "0009-0005-8230-030X"
},
{
"family_name": "Ashley",
"given_name": "Michael C. B.",
"orcid": "0000-0003-1412-2028"
},
{
"family_name": "Hankins",
"given_name": "Matthew J.",
"orcid": "0000-0001-9315-8437"
},
{
"family_name": "Moore",
"given_name": "Anna M.",
"orcid": "0000-0002-2894-6936"
},
{
"family_name": "Soon",
"given_name": "Jamie",
"orcid": "0000-0001-9226-4043"
},
{
"family_name": "Travouillon",
"given_name": "Tony",
"orcid": "0000-0001-9304-6718"
}
],
"abstract": "\n
We present a near-infrared census of stellar large-amplitude variables (LAVs) observed by the Palomar Gattini-IR (PGIR) surveyor from 2019–2021. Over the three-year time period, PGIR performed a brightness-limited survey of the Northern sky (∼18,000 deg2) to J-band AB magnitudes ∼13 within and ∼15 outside the Galactic plane. From ∼70 million stars detected in PGIR reference images, we provide a spectral and photometric library of the 128 largest amplitude stellar variables detected to median SNR > 10 for more than 50 epochs with more than 5 high-amplitude detections, peak-to-peak magnitudes ≥2, and von Neumann ratios ≤0.2. We obtained medium-resolution near-infrared spectra with TripleSpec on the 200 inch Hale Telescope at Palomar Observatory and SpeX at NASA’s Infrared Telescope Facility. The spectral census consists of 82 evolved and dust-obscured Asymptotic Giant Branch stars, 16 R Coronae Borealis stars, 13 young-stellar or pre-main-sequence objects, 8 symbiotic binaries, 7 erratic carbon- and oxygen-rich giants, and 2 RV Tauri supergiants. The spectral and photometric dataset serves as an atlas of near-infrared LAVs and a repository of evolved stars, eruptive variables, and binary systems for future deeper infrared surveys.
\n
\n
We announce a recently detected outburst that is currently only a few months old, and probably of FU Orionis type. The progenitor to the outburst was an emission-line, flat-spectrum spectral energy distribution young stellar object located in the W5 region, though somewhat outside the main star formation action. We present optical, near-infrared, and mid-infrared lightcurves that illustrate the quiescent state of [KAG2008] 13656 and its subsequent Δr ≈ −4 mag and ΔJ ≈ −3 mag outburst over ∼75 days in late-2025. Follow-up optical and near-infrared spectroscopy confirms the expected features from an FU Ori disk and outflow.
\n
\n
Magnetic fields in pre-main-sequence (PMS) stars regulate angular momentum evolution, drive magnetic activity, and modify stellar structure, yet their surface distributions remain poorly constrained. Traditional single-component Zeeman broadening analyses typically yield mean field strengths of 2–4 kG, sometimes exceeding the photospheric equipartition limit, and assume complete magnetic coverage. These assumptions conflict with evidence that strong fields are concentrated in cool starspots. Here, we present the first systematic separation of photospheric and starspot magnetic field strengths in PMS stars, using high-resolution (R ≈ 45,000) H- and K-band spectra from the Raw and Reduced IGRINS Archive. By modeling temperature and magnetic field strength simultaneously for a vetted sample of 33 classes II–III young stellar objects, we find median photospheric field strengths of 1.2 kG and median spot field strengths over 2 times stronger at 2.56 kG, resolving the apparent superequipartition tension and removing the need for a unity magnetic filling factor. Our results show that PMS surfaces are permeated by concentrated, kilogauss-strength spot fields covering 27%–83% of the visible hemisphere. This two-component framework offers a physically motivated means to reconcile spectroscopic and imaging-based magnetic diagnostics and enables large-scale magnetic population studies across young clusters and star-forming regions.
\n
Kinematic studies of young stars and star clusters have increased our understanding of the process of star formation and evolution in the Milky Way. FU Orionis objects are a specific class of young stellar object notable for their extremely high disk-to-star accretion rates. We use parallax and proper motion information from the Gaia astrometric survey to study five known FU Ori stars towards the Cygnus clouds, in the distance range ∼500–900 pc, and seek evidence of their kinematic association with proximal stellar groups or clusters. We develop multiple search criteria within the Gaia data sets to look for nearby stellar aggregates and to reliably isolate their likely member stars. We show that V1057 Cygni and HBC 722 are kinematically consistent with the 3D locations as well as the inferred proper motion fields of the North America Nebula cluster. We show a similar association of V1515 Cygni with NGC 6914 in the Cygnus-X region, and of V2494 Cygni with stars in the dark cloud LDN 1003 and Braid Nebula. Further, we find that V1735 Cygni is consistent in both position and proper motion with the streamer structure of IC 5146, and we trace the streamer's similar proper motions to the main cluster. Color–magnitude diagrams of all identified clusters show the presence of pre-main-sequence populations, strengthening the likelihood of a physical association between the young FU Ori stars and their respective nearby clusters.
",
"doi": "10.1088/1538-3873/ae078a",
"issn": "0004-6280",
"publisher": "IOP Publishing",
"publication": "Publications of the Astronomical Society of the Pacific",
"publication_date": "2025-10",
"series_number": "10",
"volume": "137",
"issue": "10",
"pages": "104204"
},
{
"id": "authors:reks7-9mm85",
"collection": "authors",
"collection_id": "reks7-9mm85",
"cite_using_url": "https://authors.library.caltech.edu/records/reks7-9mm85",
"type": "article",
"title": "Spectral Biases, Starspot Morphology, and Dynamo Transitions on the Pre-main Sequence: Insights from the X-Shooter WTTS Library",
"author": [
{
"family_name": "P\u00e9rez Paolino",
"given_name": "Facundo",
"orcid": "0000-0002-4128-7867",
"clpid": "P\u00e9rez-Paolino-Facundo"
},
{
"family_name": "Bary",
"given_name": "Jeffrey S.",
"orcid": "0000-0001-8642-5867"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Horner",
"given_name": "Benjamin"
},
{
"family_name": "Carvalho",
"given_name": "Adolfo",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo"
}
],
"abstract": "Starspots are ubiquitous in young, low-mass stars, yet their impact on the spectral classification and fundamental parameter inference of pre-main-sequence stars (PMS) has been largely overlooked. In this study, we demonstrate that cool starspots systematically distort spectral morphology and bias the effective temperatures, surface gravities, and luminosities derived for nonaccreting weak-lined T Tauri stars (WTTSs). Using a sample of 56 WTTSs with high-resolution, broadband X-Shooter spectra, we perform two-temperature spectral fits that explicitly account for spot coverages and temperature contrasts. These composite models consistently outperform traditional single-temperature fits, particularly in the 3350–4000 K regime, where spot contributions dominate the red-optical and near-IR flux. Moreover, we propose that surface gravity discrepancies between optical and IR measurements are a natural consequence of spot-dominated emission in PMS stars. We find that single-temperature models can overestimate effective temperatures by up to 700 K and underestimate log g by 1–2 dex. Using spot-corrected effective temperatures, we derive masses and ages from traditional, magnetic, and spotted evolutionary models, finding that spot corrections systematically raise inferred masses by up to 80% and stellar ages by up to 0.5 dex. These discrepancies are strongest for stars in the 0.3–0.8 M\u2299 range. Using starspots as a proxy for magnetic topology, we find evidence that a shift from largely axisymmetric to nonaxisymmetric magnetic fields dominated by small-scale structures coincides with the formation of a radiative core during PMS evolution, effectively distinguishing between the convective and interface dynamo regimes.
",
"doi": "10.3847/1538-4357/adf6ad",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-09-10",
"series_number": "2",
"volume": "990",
"issue": "2",
"pages": "205"
},
{
"id": "authors:jsa9f-ndp29",
"collection": "authors",
"collection_id": "jsa9f-ndp29",
"cite_using_url": "https://authors.library.caltech.edu/records/jsa9f-ndp29",
"type": "article",
"title": "Continued Photometric Monitoring Supports Long-term Dynamical Evolution in the Young Binary Star\u2013Disk System KH 15D",
"author": [
{
"family_name": "Lamitina",
"given_name": "Luke",
"orcid": "0009-0003-5241-2816",
"clpid": "Lamitina-Luke"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Poon",
"given_name": "Michael",
"orcid": "0000-0001-7739-9767"
}
],
"abstract": "We present photometric time series data spanning 2018–2024 that show the effects of temporal dynamics in the binary system KH 15D, a member of the NGC 2264 star-forming region. This source exhibits complex eclipsing behavior due to a precessing circumbinary disk or ring that is slightly inclined relative to the orbital plane of the binary. Using g-band and r-band observations from the Zwicky Transient Facility over seven observing seasons, we follow the evolution of the KH 15D lightcurve as it continues to emerge from its deepest observed photometric minimum about 15 yr ago. Our observations are consistent with previous models that propose a precessing, warped circumbinary disk orbiting KH 15D. We verify the gradual precession of the disk by quantifying the times of eclipse ingresses and egresses. We also examine the central rebrightening within the minima of the phased lightcurve. This feature has increased in amplitude over our observing seasons, and we measure its evolution in both amplitude and phase from year to year. Finally, we assess color as a function of phase and brightness. Our findings support the assertion that line-of-sight variations in disk density and structure, possibly due to clumping, coupled with a precessing circumbinary disk are responsible for the central rebrightening event.
",
"doi": "10.3847/1538-3881/ade2d9",
"issn": "0004-6256",
"publisher": "American Astronomical Society",
"publication": "Astronomical Journal",
"publication_date": "2025-08",
"series_number": "2",
"volume": "170",
"issue": "2",
"pages": "79"
},
{
"id": "authors:haq7z-m3446",
"collection": "authors",
"collection_id": "haq7z-m3446",
"cite_using_url": "https://authors.library.caltech.edu/records/haq7z-m3446",
"type": "article",
"title": "FUOr-Aur 0544+3330: A New Young Stellar Object Outburst in the Outskirts of Auriga OB1, Viewed Face-on",
"author": [
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
},
{
"family_name": "Stern",
"given_name": "Dan",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Connelley",
"given_name": "Michael",
"orcid": "0000-0002-8293-1428"
},
{
"family_name": "P\u00e9rez Paolino",
"given_name": "Facundo",
"orcid": "0000-0002-4128-7867",
"clpid": "P\u00e9rez-Paolino-Facundo"
},
{
"family_name": "Shetty",
"given_name": "Ahaan",
"orcid": "0009-0009-6392-4810",
"clpid": "Shetty-Ahaan"
},
{
"family_name": "Milby",
"given_name": "Zachariah",
"orcid": "0000-0001-5683-0095",
"clpid": "Milby-Zachariah"
},
{
"family_name": "Isaacson",
"given_name": "Howard",
"orcid": "0000-0002-0531-1073"
}
],
"abstract": "We present a newly appreciated FU Ori outburst event that began in 2019 and reached a peak in early 2021. Suspected young stellar object WISE J054452.25+333009.6 experienced substantial brightening, in excess of −5 mag at optical wavelengths and −2.5 mag at mid-infrared wavelengths. The time from near-quiescence to peak brightness was approximately 24 months. Optical and near-infrared spectra confirm that the outbursting source (hereby designated FUOr-Aur 0544+3330) shows all the hallmarks of the FU Ori class, including the Li i indicator of stellar youth. The mix of ionized and neutral atomic lines, alongside prominent molecular absorption features, is consistent with the expected change in spectral type from earlier in the optical to later types in the near-infrared. The closest analog among well-studied FU Ori objects is V1515 Cyg. Both sources have unusually narrow-lined absorption spectra that can be explained by a face-on disk orientation, such that disk-broadening is minimized and wind-induced blueshift (in e.g., Hα, NaD, Ca ii) is maximized. Both the optical through infrared spectral energy distribution and high-resolution spectrum are well-fit by a pure-accretion disk model. Adopting a distance of d = 1.5 kpc, the accretion and central star parameters are M \u0307 = 10^(−5.48) M\u2299 yr\u207b¹, M* = 0.17 M\u2299, and R_(inner) = 1.04 R\u2299. Other fitted values are disk inclination i = 5.9 deg and source extinction A_V = 1.83 mag. These parameters yield accretion luminosity L_(acc) = 8.4 L\u2299 and maximum disk temperature T_(max) = 6218 K.
",
"doi": "10.3847/1538-4357/ade14d",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-07-20",
"series_number": "1",
"volume": "988",
"issue": "1",
"pages": "77"
},
{
"id": "authors:0g9x9-acy35",
"collection": "authors",
"collection_id": "0g9x9-acy35",
"cite_using_url": "https://authors.library.caltech.edu/records/0g9x9-acy35",
"type": "article",
"title": "Rosette Nebula Outburst Gaia 24djk from the Young Stellar Object V557 Mon",
"author": [
{
"family_name": "Carvalho",
"given_name": "Adolfo S.",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo-S"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
}
],
"abstract": "A previously faint young stellar object (YSO), V557 Mon, rapidly brightened in late 2024 and is currently at least ΔG = 3.3 mag brighter than its typical pre-outburst brightness. The ongoing outburst is identified in the Gaia Alerts system as Gaia24djk. We obtained a 1–2.5 μm spectrum of the object and find the spectrum is dominated by line emission and continuum excess consistent with rapid YSO accretion, similar to the star EX Lup during its outburst state. We speculate that the burst, which has not yet reached its peak brightness, may become an FU Ori outburst, which would be evidenced by the emission spectrum turning into an absorption spectrum.
",
"doi": "10.3847/2515-5172/adb583",
"issn": "2515-5172",
"publisher": "American Astronomical Society",
"publication": "Research Notes of the AAS",
"publication_date": "2025-02-17",
"series_number": "2",
"volume": "9",
"issue": "2",
"pages": "38"
},
{
"id": "authors:4s7s6-npb78",
"collection": "authors",
"collection_id": "4s7s6-npb78",
"cite_using_url": "https://authors.library.caltech.edu/records/4s7s6-npb78",
"type": "article",
"title": "Ages of Stars and Planets in the Kepler Field Younger than Four Billion Years",
"author": [
{
"family_name": "Bouma",
"given_name": "Luke G.",
"orcid": "0000-0002-0514-5538",
"clpid": "Bouma-Luke-G"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Howard",
"given_name": "Andrew W.",
"orcid": "0000-0001-8638-0320",
"clpid": "Howard-A-W"
},
{
"family_name": "Isaacson",
"given_name": "Howard",
"orcid": "0000-0002-0531-1073",
"clpid": "Isaacson-Howard"
},
{
"family_name": "Masuda",
"given_name": "Kento",
"orcid": "0000-0003-1298-9699"
},
{
"family_name": "Palumbo",
"given_name": "Elsa K.",
"orcid": "0000-0001-7967-1795",
"clpid": "Palumbo-Elsa-K"
}
],
"abstract": "Recent analyses of FGK stars in open clusters have helped clarify the precision with which a star's rotation rate and lithium content can be used as empirical indicators for its age. Here we apply this knowledge to stars observed by Kepler. Rotation periods are drawn from previous work; lithium is measured from new and archival Keck/HIRES spectra. We report rotation-based ages for 23,813 stars (harboring 795 known planets) for which our method is applicable. We find that our rotational ages recover the ages of stars in open clusters spanning 0.04–2.5 Gyr; they also agree with \u227390% of the independent lithium ages. The resulting yield includes 63 planets younger than 1 Gyr at 2σ, and 109 with median ages below 1 Gyr. This is about half the number expected under the classic assumption of a uniform star formation history. The age distribution that we observe, rather than being uniform, shows that the youngest stars in the Kepler field are 3–5 times rarer than stars 3 Gyr old. This trend holds for both known planet hosts and for the parent stellar sample. We attribute this \"demographic cliff\" to a combination of kinematic heating and a declining star formation rate in the Galaxy's thin disk, and highlight its impact on the age distribution of known transiting exoplanets.
",
"doi": "10.3847/1538-4357/ad855f",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2024-12-01",
"series_number": "2",
"volume": "976",
"issue": "2",
"pages": "234"
},
{
"id": "authors:mq2s5-2mk86",
"collection": "authors",
"collection_id": "mq2s5-2mk86",
"cite_using_url": "https://authors.library.caltech.edu/records/mq2s5-2mk86",
"type": "article",
"title": "SDSS-V Local Volume Mapper (LVM): A glimpse into Orion",
"author": [
{
"family_name": "Kreckel",
"given_name": "K.",
"orcid": "0000-0001-6551-3091"
},
{
"family_name": "Egorov",
"given_name": "O. V.",
"orcid": "0000-0002-4755-118X"
},
{
"family_name": "Egorova",
"given_name": "E."
},
{
"family_name": "Blanc",
"given_name": "G. A."
},
{
"family_name": "Drory",
"given_name": "N.",
"orcid": "0000-0002-7339-3170"
},
{
"family_name": "Kounkel",
"given_name": "M.",
"orcid": "0000-0002-5365-1267"
},
{
"family_name": "M\u00e9ndez-Delgado",
"given_name": "J. E.",
"orcid": "0000-0002-6972-6411"
},
{
"family_name": "Rom\u00e1n-Z\u00fa\u00f1iga",
"given_name": "C. G.",
"orcid": "0000-0001-8600-4798"
},
{
"family_name": "S\u00e1nchez",
"given_name": "S. F."
},
{
"family_name": "Stringfellow",
"given_name": "G. S.",
"orcid": "0000-0003-1479-3059"
},
{
"family_name": "Stutz",
"given_name": "A. M."
},
{
"family_name": "Zari",
"given_name": "E.",
"orcid": "0000-0003-3769-8812"
},
{
"family_name": "Barrera-Ballesteros",
"given_name": "J. K."
},
{
"family_name": "Bizyaev",
"given_name": "D."
},
{
"family_name": "Brownstein",
"given_name": "J. R.",
"orcid": "0000-0002-8725-1069"
},
{
"family_name": "Congiu",
"given_name": "E.",
"orcid": "0000-0002-8549-4083"
},
{
"family_name": "Fern\u00e1ndez-Trincado",
"given_name": "J. G."
},
{
"family_name": "Garc\u00eda",
"given_name": "P.",
"orcid": "0000-0002-8586-6721"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Ibarra-Medel",
"given_name": "H. J.",
"orcid": "0000-0002-9790-6313"
},
{
"family_name": "Jin",
"given_name": "Y."
},
{
"family_name": "Johnston",
"given_name": "E. J.",
"orcid": "0000-0002-2368-6469"
},
{
"family_name": "Jones",
"given_name": "A. M.",
"orcid": "0000-0002-2262-8240"
},
{
"family_name": "Kim",
"given_name": "J. Serena",
"orcid": "0000-0001-6072-9344"
},
{
"family_name": "Kollmeier",
"given_name": "J. A.",
"orcid": "0000-0001-9852-1610"
},
{
"family_name": "Kong",
"given_name": "S.",
"orcid": "0000-0002-8469-2029"
},
{
"family_name": "Krishnarao",
"given_name": "D."
},
{
"family_name": "Kumari",
"given_name": "N.",
"orcid": "0000-0002-5320-2568"
},
{
"family_name": "Li",
"given_name": "J.",
"orcid": "0000-0002-4825-9367"
},
{
"family_name": "Long",
"given_name": "K. S.",
"orcid": "0000-0002-4134-864X"
},
{
"family_name": "Mata-S\u00e1nchez",
"given_name": "A."
},
{
"family_name": "Mej\u00eda-Narv\u00e1ez",
"given_name": "A.",
"orcid": "0000-0002-8931-2398"
},
{
"family_name": "Popa",
"given_name": "S. A.",
"orcid": "0009-0006-3186-5826"
},
{
"family_name": "Rix",
"given_name": "H.-W."
},
{
"family_name": "Sattler",
"given_name": "N.",
"orcid": "0000-0002-8883-6018"
},
{
"family_name": "Serna",
"given_name": "J.",
"orcid": "0000-0001-7351-6540"
},
{
"family_name": "Singh",
"given_name": "A.",
"orcid": "0009-0000-3962-103X"
},
{
"family_name": "S\u00e1nchez-Gallego",
"given_name": "J. R.",
"orcid": "0000-0003-2486-3858"
},
{
"family_name": "Wofford",
"given_name": "A."
},
{
"family_name": "Wong",
"given_name": "T.",
"orcid": "0000-0002-7759-0585"
}
],
"abstract": "Context. The Orion Molecular Cloud complex, one of the nearest (D = 406 pc) and most extensively studied massive star-forming regions, is ideal for constraining the physics of stellar feedback, but its ~12 deg diameter on the sky requires a dedicated approach to mapping ionized gas structures within and around the nebula. Aims. The Sloan Digital Sky Survey (SDSS-V) Local Volume Mapper (LVM) is a new optical integral field unit (IFU) that will map the ionized gas within the Milky Way and Local Group galaxies, covering 4300 deg² of the sky with the new LVM Instrument (LMV-I). Methods. We showcase optical emission line maps from LVM covering 12 deg² inside of the Orion belt region, with 195 000 individual spectra combined to produce images at 0.07 pc (35.3″) resolution. This is the largest IFU map made (to date) of the Milky Way, and contains well-known nebulae (the Horsehead Nebula, Flame Nebula, IC 434, and IC 432), as well as ionized interfaces with the neighboring dense Orion B molecular cloud. Results. We resolve the ionization structure of each nebula, and map the increase in both the [S II]/Hα and [N II]/Hα line ratios at the outskirts of nebulae and along the ionization front with Orion B. [O III] line emission is only spatially resolved within the center of the Flame Nebula and IC 434, and our ~0.1 pc scale line ratio diagrams show how variations in these diagnostics are lost as we move from the resolved to the integrated view of each nebula. We detect ionized gas emission associated with the dusty bow wave driven ahead of the star σ Orionis, where the stellar wind interacts with the ambient interstellar medium. The Horsehead Nebula is seen as a dark occlusion of the bright surrounding photo-disassociation region. This small glimpse into Orion only hints at the rich science that will be enabled by the LVM.
",
"doi": "10.1051/0004-6361/202449943",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2024-09",
"volume": "689",
"pages": "A352"
},
{
"id": "authors:w29yg-ez711",
"collection": "authors",
"collection_id": "w29yg-ez711",
"cite_using_url": "https://authors.library.caltech.edu/records/w29yg-ez711",
"type": "article",
"title": "Kinematic Association of Two FU Orionis Stars with Young Clusters in Orion",
"author": [
{
"family_name": "Roychowdhury",
"given_name": "Tamojeet",
"orcid": "0009-0003-9906-2745",
"clpid": "Roychowdhury-Tamojeet"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
}
],
"abstract": "\n
Many known FU Orionis stars are projected on the sky at the peripheries of star-forming regions. Physical association is assumed, but not yet firmly established. We investigate the cases of two such stars, FU Ori and V883 Ori, seeking kinematic evidence of their membership in young clusters associated with the Orion molecular clouds. Using astrometric data from Gaia DR3, we search for consistent 2D velocities, and we also use more limited radial velocity data to assess 3D velocities. Considering +/ − 25 pc boxes centered on λ Ori and the Orion Nebula Cluster, we use the inferred velocity fields to confirm the kinematic association of FU Ori with the former, and V883 Ori with the latter.
\n
\n
Accurate age and mass determinations for young pre-main-sequence stars are made challenging by the presence of large-scale starspots. We present results from a near-infrared spectroscopic survey of 10 T-Tauri Stars in Taurus-Auriga that characterize spot-filling factors and temperatures, the resulting effects on temperature and luminosity determinations, and the consequences for inferred stellar masses and ages. We constructed composite models of spotted stars by combining BTSettl-CIFIST synthetic spectra of atmospheres to represent the spots and the photosphere along with continuum emission from a warm inner disk. Using a Markov Chain Monte Carlo algorithm, we find the best-fit spot and photospheric temperatures, spot-filling factors, as well as disk-filling factors. This methodology allowed us to reproduce the 0.75–2.40 μm stellar spectra and molecular feature strengths for all of our targets, disentangling the complicated multicomponent emission. For a subset of stars with multiepoch observations spanning an entire stellar rotation, we correlate the spectral variability and changes in the filling factors with rotational periods observed in K2 and AAVSO photometry. Combining spot-corrected effective temperatures and Gaia distances, we calculate luminosities and use the Stellar Parameters of Tracks with Starspots models to infer spot-corrected masses and ages for our sample of stars. Our method of accounting for spots results in an average increase of 60% in mass and a doubling in age with respect to traditional methods using optical spectra that do not account for the effect of spots.
\n
\n
Sun-like stars are thought to accrete most of their final mass during the protostellar phase, during which the stellar embryo is surrounded by an infalling dense envelope. We present an analysis of 26 K-band spectra of Class 0 protostars, which are the youngest protostars. Of these, 18 are new observations made with the Keck MOSFIRE instrument. H i Brγ, several H2, and CO Δv = 2 features are detected and analyzed. We detect Brγ emission in 62%, CO overtone emission in 50%, and H2 emission in 90% of sources. The H i and CO emission is associated with accretion, while the H2 lines are consistent with shock excitation indicating jets/outflows. Six objects exhibit photospheric absorption features, with almost no outflow activity and no detection of the accretion-related Brγ emission line. Comparing these results with an archival sample of Class I K-band spectra, we find that the CO and Brγ emission lines are systematically more luminous in Class 0s, suggesting that the accretion is on average more vigorous in the Class 0 phase. Typically associated with the heated inner accretion disk, the much higher detection rate of CO overtone emission in Class 0s indicates also that episodes of high accretion activity are more frequent in Class 0 systems. The kinematics of the Class 0 CO overtone emission suggest either an accretion-heated inner disk or material directly infalling onto the central region. This could point toward an accretion mechanism of different nature in Class 0 systems than the typical picture of magnetospheric accretion.
\n
\n
Monoceros R2 (Mon R2) is one of the closest large active star-forming regions. This extremely young and partially embedded region provides an excellent laboratory for studying star formation and the early evolution of young stellar objects (YSOs). In this paper, we conduct an optical study of the greater Mon R2 region. Beginning with 1690 previously identified candidate YSOs, we used 496 sources with good proper motions and parallaxes from Gaia Data Release (DR) 3 to determine the astrometric properties for likely members of Mon R2. We then used both astrometric and photometric (isochronal and variability) criteria to determine that 308 of these stars are highly probable members. Using the same criteria, we considered a broad area search around Mon R2 in Gaia DR3 and separated candidate members from field stars. In total, we selected 651 likely new cluster members that had been missed in the previous X-ray and infrared excess selection techniques used in the past to establish cluster membership. Revised astrometric properties of the cluster were found using the combined sample of ∼959 highly probable member stars. For the literature plus the new candidate member list, optical light curves were compiled from the Zwicky Transient Facility. For 470 identified variable sources, we attempted classification based on the flux asymmetry (M) and quasiperiodicity (Q) metrics. We find that Mon R2 is dominated by quasiperiodic symmetric variables, with aperiodic sources also a significant population. A few tens of large-amplitude variables are identified that may be of interest for further study.
\n
\n
The classification of variable objects provides insight into a wide variety of astrophysics ranging from stellar interiors to galactic nuclei. The Zwicky Transient Facility (ZTF) provides time-series observations that record the variability of more than a billion sources. The scale of these data necessitates automated approaches to make a thorough analysis. Building on previous work, this paper reports the results of the ZTF Source Classification Project (SCoPe), which trains neural network and XGBoost (XGB) machine-learning (ML) algorithms to perform dichotomous classification of variable ZTF sources using a manually constructed training set containing 170,632 light curves. We find that several classifiers achieve high precision and recall scores, suggesting the reliability of their predictions for 209,991,147 light curves across 77 ZTF fields. We also identify the most important features for XGB classification and compare the performance of the two ML algorithms, finding a pattern of higher precision among XGB classifiers. The resulting classification catalog is available to the public, and the software developed for SCoPe is open source and adaptable to future time-domain surveys.
\n
\n
Complex periodic variables (CPVs) are stars that exhibit highly structured and periodic optical light curves. Previous studies have indicated that these stars are typically disk-free pre-main-sequence M dwarfs with rotation periods ranging from 0.2 to 2 days. To advance our understanding of these enigmatic objects, we conducted a blind search using TESS 2 minute data of 65,760 K and M dwarfs with T<16 mag and d<150 pc. We found 50 high-quality CPVs, and subsequently determined that most are members of stellar associations. Among the new discoveries are the brightest (T ≈ 9.5 mag), closest (d ≈ 20 pc), and oldest (≈200 Myr) CPVs known. One exceptional object, LP 12-502, exhibited up to eight flux dips per cycle. Some of these dips coexisted with slightly different periods, and the shortest-duration dips precisely matched the expected timescale for transiting small bodies at the corotation radius. Broadly, our search confirms that CPVs are mostly young (\u2272150 Myr) and low-mass (\u22720.4 M\u2299). The flux dips characteristic of the class have lifetimes of ≈100 cycles, although stellar flares seem to induce a sudden dip collapse once every few months. The most plausible explanation for these phenomena remains corotating concentrations of gas or dust. The gas or dust is probably entrained by the star's magnetic field, and the sharp features could result from a multipolar field topology, a hypothesis supported by correspondences between the light curves of CPVs and of rapidly rotating B stars known to have multipolar magnetic fields.
\n
Abstract We follow up our photometric study of the postoutburst evolution of the FU Ori object V960 Mon with a complementary spectroscopic study at high dispersion that uses time series spectra from the Keck/HIgh Resolution Echelle Spectrograph. Consistent with the photometric results reported in Carvalho et al., we find that the spectral evolution of V960 Mon corresponds to a decrease in the temperature of the inner disk, driven by a combination of a decreasing accretion rate and an increasing inner disk radius. We also find that although the majority of the absorption lines are well matched by our accretion disk model spectrum, there are several strong absorption line families and a few emission lines that are not captured by the model. By subtracting the accretion disk model from the data at each epoch, we isolate the wind and outflow components of the system. The residuals show both broad and highly blueshifted profiles, as well as narrow and only slightly blueshifted profiles, with some lines displaying both types of features.
",
"doi": "10.3847/1538-4357/acff59",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2023-12-01",
"series_number": "2",
"volume": "958",
"issue": "2",
"pages": "140"
},
{
"id": "authors:70abh-k7e33",
"collection": "authors",
"collection_id": "70abh-k7e33",
"cite_using_url": "https://authors.library.caltech.edu/records/70abh-k7e33",
"type": "article",
"title": "RNO 54: A Previously Unappreciated FU Ori Star",
"author": [
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Carvalho",
"given_name": "Adolfo",
"orcid": "0000-0002-9540-853X",
"clpid": "Carvalho-Adolfo"
},
{
"family_name": "van Roestel",
"given_name": "Jan",
"orcid": "0000-0002-2626-2872",
"clpid": "van-Roestel-Jan"
},
{
"family_name": "De",
"given_name": "Kishalay",
"orcid": "0000-0002-8989-0542",
"clpid": "De-Kishalay"
}
],
"abstract": "We present evidence in support of the hypothesis that the young stellar object RNO 54 is a mature-stage FU Ori type source. The star was first cataloged as a \"red nebulous object\" in the 1980s but appears to have undergone its outburst prior to the 1890s. Present-day optical and near-infrared spectra are consistent with those of other FU Ori-type stars, both in the details of spectral line presence and shape, and in the overall change in spectral type from an FGK-type in the optical, to the M-type presented in the near-infrared. In addition, the spectral energy distribution of RNO 54 is well-fit by a pure-accretion disk model with parameters: \u1e40 = 10 \u2212 3.45 \u00b1 0.06 M_\u2299 yr\u207b\u00b9, M* = 0.23 \u00b1 0.06 M_\u2299, and R_(inner) = 3.68 \u00b1 0.76 R_\u2299, though we believe R inner is likely close to its upper range of 4.5 R_\u2299 in order to produce a T\u2098\u2090\u2093 = 7000 K that is consistent with the optical to near-infrared spectra. The resulting L_(acc) is \u223c265 L_\u2299. To find these values, we adopted a source distance d = 1400 pc and extinction A\u1d65 = 3.9 mag, along with disk inclination i = 50 deg based on the consideration of confidence intervals from our initial disk model, and in agreement with observational constraints. The new appreciation of a well-known source as an FU Ori-type object suggests that other such examples may be lurking in extant samples.
",
"doi": "10.3847/2041-8213/ad0be0",
"issn": "2041-8205",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal Letters",
"publication_date": "2023-12-01",
"series_number": "2",
"volume": "958",
"issue": "2",
"pages": "L27"
},
{
"id": "authors:gsfxm-3qx92",
"collection": "authors",
"collection_id": "gsfxm-3qx92",
"cite_using_url": "https://authors.library.caltech.edu/records/gsfxm-3qx92",
"type": "article",
"title": "Twenty-five Years of Accretion onto the Classical T Tauri Star TW Hya",
"author": [
{
"family_name": "Herczeg \u6c88",
"given_name": "Gregory J. \u96f7\u6b4c",
"orcid": "0000-0002-7154-6065",
"clpid": "Herczeg-Gregory-J"
},
{
"family_name": "Chen \u9648",
"given_name": "Yuguang \u6631\u5149",
"orcid": "0000-0003-4520-5395"
},
{
"family_name": "Donati",
"given_name": "Jean-Francois",
"orcid": "0000-0001-5541-2887"
},
{
"family_name": "Dupree",
"given_name": "Andrea K.",
"orcid": "0000-0002-8985-8489"
},
{
"family_name": "Walter",
"given_name": "Frederick M.",
"orcid": "0000-0001-7796-1756"
},
{
"family_name": "Hillenbrand",
"given_name": "Lynne A.",
"clpid": "Hillenbrand-L-A"
},
{
"family_name": "Johns-Krull",
"given_name": "Christopher M.",
"orcid": "0000-0002-8828-6386"
},
{
"family_name": "Manara",
"given_name": "Carlo F.",
"orcid": "0000-0003-3562-262X"
},
{
"family_name": "G\u00fcnther",
"given_name": "Hans Moritz",
"orcid": "0000-0003-4243-2840"
},
{
"family_name": "Fang \u623f",
"given_name": "Min \u654f",
"orcid": "0000-0001-8060-1321"
},
{
"family_name": "Schneider",
"given_name": "P. Christian",
"orcid": "0000-0002-5094-2245"
},
{
"family_name": "Valenti",
"given_name": "Jeff A.",
"orcid": "0000-0003-3305-6281"
},
{
"family_name": "Alencar",
"given_name": "Silvia H. P.",
"orcid": "0000-0002-5171-8376"
},
{
"family_name": "Venuti",
"given_name": "Laura",
"orcid": "0000-0002-4115-0318"
},
{
"family_name": "Alcal\u00e1",
"given_name": "Juan Manuel",
"orcid": "0000-0001-8657-095X"
},
{
"family_name": "Frasca",
"given_name": "Antonio",
"orcid": "0000-0002-0474-0896"
},
{
"family_name": "Arulanantham",
"given_name": "Nicole",
"orcid": "0000-0003-2631-5265"
},
{
"family_name": "Linsky",
"given_name": "Jeffrey L.",
"orcid": "0000-0003-4446-3181"
},
{
"family_name": "Bouvier",
"given_name": "Jerome",
"orcid": "0000-0002-7450-6712"
},
{
"family_name": "Brickhouse",
"given_name": "Nancy S.",
"orcid": "0000-0002-8704-4473"
},
{
"family_name": "Calvet",
"given_name": "Nuria",
"orcid": "0000-0002-3950-5386"
},
{
"family_name": "Espaillat",
"given_name": "Catherine C.",
"orcid": "0000-0001-9227-5949"
},
{
"family_name": "Campbell-White",
"given_name": "Justyn",
"orcid": "0000-0002-3913-3746"
},
{
"family_name": "Carpenter",
"given_name": "John M.",
"orcid": "0000-0003-2251-0602"
},
{
"family_name": "Chang",
"given_name": "Seok-Jun",
"orcid": "0000-0002-0112-5900"
},
{
"family_name": "Cruz",
"given_name": "Kelle L.",
"orcid": "0000-0002-1821-0650"
},
{
"family_name": "Dahm",
"given_name": "S. E.",
"orcid": "0000-0002-2968-2418"
},
{
"family_name": "Eisl\u00f6ffel",
"given_name": "Jochen",
"orcid": "0000-0001-6496-0252"
},
{
"family_name": "Edwards",
"given_name": "Suzan",
"orcid": "0000-0002-3232-665X"
},
{
"family_name": "Fischer",
"given_name": "William J.",
"orcid": "0000-0002-3747-2496"
},
{
"family_name": "Guo \u90ed",
"given_name": "Zhen \u9707",
"orcid": "0000-0003-0292-4832"
},
{
"family_name": "Henning",
"given_name": "Thomas",
"orcid": "0000-0002-1493-300X"
},
{
"family_name": "Ji \u7eaa",
"given_name": "Tao \u6d9b"
},
{
"family_name": "Jose",
"given_name": "Jessy",
"orcid": "0000-0003-4908-4404"
},
{
"family_name": "Kastner",
"given_name": "Joel H.",
"orcid": "0000-0002-3138-8250"
},
{
"family_name": "Launhardt",
"given_name": "Ralf",
"orcid": "0000-0002-8298-2663"
},
{
"family_name": "Principe",
"given_name": "David A.",
"orcid": "0000-0002-7939-377X"
},
{
"family_name": "Robinson",
"given_name": "Connor E.",
"orcid": "0000-0003-1639-510X"
},
{
"family_name": "Serna",
"given_name": "Javier",
"orcid": "0000-0001-7351-6540"
},
{
"family_name": "Siwak",
"given_name": "Michal",
"orcid": "0000-0002-0786-7307"
},
{
"family_name": "Sterzik",
"given_name": "Michael F.",
"orcid": "0000-0002-5784-4437"
},
{
"family_name": "Takasao",
"given_name": "Shinsuke",
"orcid": "0000-0003-3882-3945"
}
],
"abstract": "\n
Accretion plays a central role in the physics that governs the evolution and dispersal of protoplanetary disks. The primary goal of this paper is to analyze the stability over time of the mass accretion rate onto TW Hya, the nearest accreting solar-mass young star. We measure veiling across the optical spectrum in 1169 archival high-resolution spectra of TW Hya, obtained from 1998–2022. The veiling is then converted to accretion rate using 26 flux-calibrated spectra that cover the Balmer jump. The accretion rate measured from the excess continuum has an average of 2.51 × 10−9M\u2299 yr−1 and a Gaussian distribution with an FWHM of 0.22 dex. This accretion rate may be underestimated by a factor of up to 1.5 because of uncertainty in the bolometric correction and another factor of 1.7 because of excluding the fraction of accretion energy that escapes in lines, especially Lyα. The accretion luminosities are well correlated with He line luminosities but poorly correlated with Hα and Hβ luminosity. The accretion rate is always flickering over hours but on longer timescales has been stable over 25 years. This level of variability is consistent with previous measurements for most, but not all, accreting young stars.
\n