[
{
"id": "authors:ex9a8-5ak48",
"collection": "authors",
"collection_id": "ex9a8-5ak48",
"cite_using_url": "https://authors.library.caltech.edu/records/ex9a8-5ak48",
"type": "article",
"title": "Transient Relativistic Iron Emission Line from an X-Ray Flaring Supermassive Black Hole",
"author": [
{
"family_name": "Zhao",
"given_name": "Xiurui",
"orcid": "0000-0002-7791-3671",
"clpid": "Zhao-Xiurui"
},
{
"family_name": "Ajello",
"given_name": "Marco",
"orcid": "0000-0002-6584-1703"
},
{
"family_name": "Civano",
"given_name": "Francesca",
"orcid": "0000-0002-2115-1137"
},
{
"family_name": "Garc\u00eda",
"given_name": "Javier A.",
"orcid": "0000-0003-3828-2448",
"clpid": "Garc\u00eda-Javier-A"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Marchesi",
"given_name": "Stefano",
"orcid": "0000-0001-5544-0749"
},
{
"family_name": "Shen",
"given_name": "Yue",
"orcid": "0000-0003-1659-7035"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Yang",
"given_name": "Qian",
"orcid": "0000-0002-6893-3742"
},
{
"family_name": "Boorman",
"given_name": "Peter G.",
"orcid": "0000-0001-9379-4716",
"clpid": "Boorman-Peter-G"
},
{
"family_name": "Harrison",
"given_name": "Fiona",
"orcid": "0000-0002-4226-8959",
"clpid": "Harrison-F-A"
},
{
"family_name": "Kara",
"given_name": "Erin",
"orcid": "0000-0003-0172-0854"
},
{
"family_name": "Pizzetti",
"given_name": "Andrealuna",
"orcid": "0000-0001-6412-2312"
},
{
"family_name": "Silver",
"given_name": "Ross",
"orcid": "0000-0001-6564-0517"
},
{
"family_name": "Sokolovsky",
"given_name": "Kirill V.",
"orcid": "0000-0001-5991-6863"
},
{
"family_name": "Stone",
"given_name": "Zachary",
"orcid": "0000-0002-8501-3518"
},
{
"family_name": "Torres-Alb\u00e0",
"given_name": "Nuria",
"orcid": "0000-0003-3638-8943"
},
{
"family_name": "Wu",
"given_name": "Qiaoya",
"orcid": "0000-0003-4202-1232"
},
{
"family_name": "Zhu",
"given_name": "Peixin",
"orcid": "0000-0002-1333-147X"
}
],
"abstract": "\n
We report the discovery of the first transient relativistic iron Kα line in an active galactic nucleus (AGN), J1047+5907. The line was detected 21.5 days (rest frame) after an X-ray coronal flare was observed in 2008, and it exhibits significant broadening consistent with relativistic reflection from the accretion disk in the vicinity of the central supermassive black hole (SMBH). The line has a width of ∼300 eV, corresponding to a Keplerian velocity of 14,000 km s−1, at a distance of 5–41 light-days from the SMBH, strongly implying that the observed coronal flare triggered the emergence of the line. This event provides rare direct evidence of the response of the accretion disk to impulsive coronal illumination and offers a new method to probe the SMBH and disk physics. The relativistic modeling favors a broadened line produced by distant reflection from an accretion disk around a rapidly spinning black hole viewed at an intermediate inclination, consistent with other observations. Systematic monitoring of type 1 AGN following strong X-ray flares may open a new observational window into the innermost regions of AGN, enabling constraints on the physics of SMBH and its accretion disk at different radii that are otherwise challenging to access.
\n
Context. Active galactic nuclei (AGNs) exhibit significant variability across the electromagnetic spectrum on a wide range of timescales. This variability is particularly extreme in the X–ray band, showing both high-amplitude and rapid fluctuations. Power spectral density (PSD) analysis is a common tool used to characterise the observed variability in these objects. Although PSDs of AGN are typically well described by a bending power-law model, the dependence of the model parameters on photon energy has not been systematically explored in the past.
\nAims. Our objective is to investigate whether the PSD parameters of AGNs depend on energy, considering two low-mass Seyfert galaxies – NGC 4051 and NGC 4395 – as case studies. Both sources are highly variable in X-rays, and they have been observed extensively with current and past X-ray satellites. Using all archival observations, we aim to measure their power spectra over a broad frequency and energy range and investigate if and how the power spectrum evolves with energy.
\nMethods. We used archival data from XMM-Newton, Suzaku, and NuSTAR, and computed the power spectrum in six energy bands from 0.3 to 20 keV. Then we fitted the power spectra with a bending power-law model and investigated the energy dependence of the model parameters.
\nResults. The power spectra computed using light curves taken from different satellites and at different times are consistent within the errors, indicating that the X-ray variability process is stationary in these two objects. We found that, for both sources: a) the PSD bending frequency remains constant with the energy, b) the high-frequency slope becomes flatter with increasing energy, and c) the power spectrum amplitude decreases with increasing energy.
\nConclusions. Our results can significantly constrain current models that explain the variability of X-rays in AGNs (such as the fluctuating accretion rate model). Similar studies of more AGNs are necessary to quantify in detail the energy dependence of the power spectrum in AGNs.
",
"doi": "10.1051/0004-6361/202557606",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2026-03",
"volume": "707",
"pages": "A180"
},
{
"id": "authors:txkc7-wz840",
"collection": "authors",
"collection_id": "txkc7-wz840",
"cite_using_url": "https://authors.library.caltech.edu/records/txkc7-wz840",
"type": "article",
"title": "XRISM Finds the Changing-look Active Galactic Nucleus NGC 1365 in an Extended Low State: A Dense, Highly Ionized Outflow Obscures the Central Source",
"author": [
{
"family_name": "Zaidouni",
"given_name": "Fatima",
"orcid": "0000-0003-0931-0868"
},
{
"family_name": "Kara",
"given_name": "Erin",
"orcid": "0000-0003-0172-0854"
},
{
"family_name": "Kosec",
"given_name": "Peter",
"orcid": "0000-0003-4511-8427"
},
{
"family_name": "Behar",
"given_name": "Ehud",
"orcid": "0000-0001-9735-4873"
},
{
"family_name": "Mushotzky",
"given_name": "Richard",
"orcid": "0000-0002-7962-5446"
},
{
"family_name": "Koss",
"given_name": "Michael",
"orcid": "0000-0002-7998-9581"
},
{
"family_name": "Jur\u00e1\u0148ov\u00e1",
"given_name": "A.",
"orcid": "0000-0002-7292-6852"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Brenneman",
"given_name": "Laura W.",
"orcid": "0000-0003-2663-1954"
},
{
"family_name": "Chakraborty",
"given_name": "Joheen",
"orcid": "0000-0002-0568-6000"
},
{
"family_name": "Ebisawa",
"given_name": "Ken",
"orcid": "0000-0002-5352-7178"
},
{
"family_name": "Eckart",
"given_name": "Megan E.",
"orcid": "0000-0003-3894-5889"
},
{
"family_name": "Fabian",
"given_name": "Andrew C.",
"orcid": "0000-0002-9378-4072"
},
{
"family_name": "Fukazawa",
"given_name": "Yasushi",
"orcid": "0000-0002-0921-8837"
},
{
"family_name": "Garc\u00eda",
"given_name": "Javier A.",
"orcid": "0000-0003-3828-2448",
"clpid": "Garc\u00eda-Javier-A"
},
{
"family_name": "Gu",
"given_name": "Liyi",
"orcid": "0000-0001-9911-7038"
},
{
"family_name": "Masterson",
"given_name": "Megan",
"orcid": "0000-0003-4127-0739"
},
{
"family_name": "Ogawa",
"given_name": "Shoji",
"orcid": "0000-0002-5701-0811"
},
{
"family_name": "Okajima",
"given_name": "Takashi",
"orcid": "0000-0002-6054-3432"
},
{
"family_name": "Paltani",
"given_name": "St\u00e9phane",
"orcid": "0000-0002-8108-9179"
},
{
"family_name": "Rogantini",
"given_name": "Daniele",
"orcid": "0000-0002-5359-9497"
},
{
"family_name": "Terashima",
"given_name": "Yuichi",
"orcid": "0000-0003-1780-5481"
},
{
"family_name": "Williams",
"given_name": "Brian J.",
"orcid": "0000-0003-2063-381X"
},
{
"family_name": "Yamada",
"given_name": "Satoshi",
"orcid": "0000-0002-9754-3081"
}
],
"abstract": "\n
We present the first XRISM/Resolve observations of the active galactic nucleus NGC 1365, obtained in 2024 February and July. NGC 1365 is known for rapid transitions between Compton-thick and Compton-thin states, along with strong absorption from a highly ionized wind. During our observations, the source was found in a persistent low-flux state, characterized by a decrease in hard-X-ray luminosity and significant line-of-sight obscuration. In this state, XRISM/Resolve reveals clear Fe xxv and Fe xxvi absorption lines together with, for the first time in this source, corresponding emission lines. These features may arise either from reemission from a photoionized wind (P Cygni profile) or from collisionally ionized gas associated with outflow-driven shocks in the interstellar medium. We estimate the wind launch radius to be approximately 1016 cm (∼104Rg), consistent with the location of the X-ray broadline region. We also resolve a broadened Fe Kα line by σ ∼ 1300 km s−1, placing it at similar scales to the wind, consistent with radii inferred from disk-broadening models and the variability of the Fe Kα broad line. The similarity of the Fe Kα profile to the Hβ wing and broad Paα width indicates that the X-ray-emitting region is likely cospatial with the optical/infrared broadline region and originates from the same gas.
\n
Recent intensive monitoring campaigns of active galactic nuclei have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations revealed a strong correlation between the UV and optical variability, but a weaker correlation between the X-ray and UV bands. This challenges the standard X-ray reprocessing scenario. We revisit the X-ray/UV connection in NGC 5548 by fitting archival 2014 HST and Swift /XRT light curves assuming X-ray reverberation from a dynamically evolving X-ray corona. Our results show that as long as the corona height, photon index, and power vary over time, X-ray reverberation can explain the observed UV and optical variability within 2% and 5%, respectively (on average). The evolution of the best-fit parameters suggests that fast changes in coronal geometry and energetics on a timescale of days are required to explain the observed variability.
",
"doi": "10.1051/0004-6361/202557643",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy & Astrophysics",
"publication_date": "2026-01",
"volume": "705",
"pages": "A257"
},
{
"id": "authors:svpgf-g1484",
"collection": "authors",
"collection_id": "svpgf-g1484",
"cite_using_url": "https://authors.library.caltech.edu/records/svpgf-g1484",
"type": "article",
"title": "Revisiting the X-ray-to-UV relation of quasars in the era of all-sky surveys",
"author": [
{
"family_name": "Chira",
"given_name": "Maria",
"orcid": "0000-0003-3116-9258"
},
{
"family_name": "Georgakakis",
"given_name": "Antonis",
"orcid": "0000-0002-3514-2442"
},
{
"family_name": "Ruiz",
"given_name": "Angel",
"orcid": "0000-0002-3352-4383"
},
{
"family_name": "Chen",
"given_name": "Shi-Jiang",
"orcid": "0009-0004-9950-9807"
},
{
"family_name": "Buchner",
"given_name": "Johannes"
},
{
"family_name": "Rankine",
"given_name": "Amy L",
"orcid": "0000-0002-2091-1966"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Aydar",
"given_name": "Catarina"
},
{
"family_name": "Salvato",
"given_name": "Mara",
"orcid": "0000-0001-7116-9303"
},
{
"family_name": "Merloni",
"given_name": "Andrea"
},
{
"family_name": "Krumpe",
"given_name": "Mirko"
}
],
"abstract": "The X-ray-to-UV relation of active galactic nuclei (AGNs), commonly parametrized via the monochromatic luminosities at 2500 Å and 2 keV, reflects the energetic interplay between the accretion disc and the X-ray-emitting corona, and is key for understanding accretion physics. Previous studies suggest that disc-dominated emission becomes more prominent with increasing optical luminosity. However, the redshift evolution of this relation remains debated, and a dependence on Eddington ratio, predicted by accretion flow models, is still observationally unconstrained. We revisit this relation using a large nearly all-sky sample by combining the Sloan Digital Sky Survey Quasar Catalog Data Release 16 quasar (QSO) catalogue with X-ray data from XMM–Newton and the SRG/eROSITA All-Sky Survey Data Release 1, yielding 136 745 QSOs at redshifts \u20600.5 ≤ z < 3.0. We introduce a hierarchical Bayesian framework that treats X-ray detections and upper limits uniformly, enabling robust inference from both parametric and non-parametric models. We confirm a tight sublinear log L_X(2 keV) – Log L_V(2500 Å) correlation, but with a normalization at the lower end of previous estimates. Contrary to most literature results, we detect a mild but systematic redshift evolution: the relation flattens and its intrinsic scatter decreases at higher redshift. This trend is consistent with disc emission increasingly dominated by scattering and enhanced energy transfer to the X-ray corona, potentially indicating redshift evolution in the X-ray bolometric correction. We find no significant dependence on Eddington ratio, in tension with recent accretion flow models.
",
"doi": "10.1093/mnras/staf1905",
"issn": "0035-8711",
"publisher": "Royal Astronomical Society",
"publication": "Monthly Notices of the Royal Astronomical Society",
"publication_date": "2026-01",
"series_number": "1",
"volume": "545",
"issue": "1",
"pages": "staf1905"
},
{
"id": "authors:ysqnz-nqk06",
"collection": "authors",
"collection_id": "ysqnz-nqk06",
"cite_using_url": "https://authors.library.caltech.edu/records/ysqnz-nqk06",
"type": "article",
"title": "The 2025 Failed Outburst of IGR J17091\u22123624: Spectral Evolution and the Role of Ionized Absorbers",
"author": [
{
"family_name": "Adegoke",
"given_name": "Oluwashina K.",
"orcid": "0000-0002-5966-4210",
"clpid": "Adegoke-Oluwashina-K"
},
{
"family_name": "Garc\u00eda",
"given_name": "Javier A.",
"orcid": "0000-0003-3828-2448",
"clpid": "Garc\u00eda-Javier-A"
},
{
"family_name": "Mastroserio",
"given_name": "Guglielmo",
"orcid": "0000-0003-4216-7936"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Connors",
"given_name": "Riley M. T.",
"orcid": "0000-0002-8908-759X"
},
{
"family_name": "Steiner",
"given_name": "James F.",
"orcid": "0000-0002-5872-6061"
},
{
"family_name": "Harrison",
"given_name": "Fiona A.",
"orcid": "0000-0003-2992-8024",
"clpid": "Harrison-F-A"
},
{
"family_name": "Buisson",
"given_name": "Douglas J. K.",
"orcid": "0000-0002-5341-6929"
},
{
"family_name": "Coley",
"given_name": "Joel B.",
"orcid": "0000-0001-7532-8359"
},
{
"family_name": "Coughenour",
"given_name": "Benjamin M.",
"orcid": "0000-0003-0870-6465"
},
{
"family_name": "Dauser",
"given_name": "Thomas",
"orcid": "0000-0003-4583-9048"
},
{
"family_name": "Ewing",
"given_name": "Melissa",
"orcid": "0000-0001-9349-8271"
},
{
"family_name": "Ingram",
"given_name": "Adam",
"orcid": "0000-0002-5311-9078"
},
{
"family_name": "Kara",
"given_name": "Erin",
"orcid": "0000-0003-0172-0854"
},
{
"family_name": "Nathan",
"given_name": "Edward",
"orcid": "0000-0002-9633-9193"
},
{
"family_name": "Parra",
"given_name": "Maxime",
"orcid": "0009-0003-8610-853X"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Tomsick",
"given_name": "John A.",
"orcid": "0000-0001-5506-9855"
}
],
"abstract": "\n
IGR J17091−3624 is the only black hole X-ray binary candidate—aside from the well-studied black hole system GRS 1915+105—observed to exhibit a wide range of structured variability patterns in its light curves. In 2025, the source underwent a “failed” outburst: it brightened in the hard state but did not transition to the soft state before returning to quiescence within a few weeks. During this period, IGR J17091−3624 was observed by multiple ground- and space-based facilities. Here, we present results from six pointed NuSTAR observations obtained during the outburst. None of the NuSTAR light curves showed the exotic variability classes typical of the soft state in this source; however, we detected, for the first time, strong dips in the count rate during one epoch, with a total duration of ∼4 ks as seen by NuSTAR. Through spectral and timing analysis of all six epochs, we investigate the hard-state spectral evolution and the nature of the dips. A clear evolution of the coronal properties with luminosity is observed over all six epochs, with clear signatures of relativistic disk reflection that remain largely unchanged across the first five epochs. The first five epochs also show a strong and stable quasiperiodic oscillation feature in the power spectra. The dips observed in Epoch 5 are consistent with partial obscuration by ionized material with a column density NH ≈ 2.0 × 1023 cm−2. We discuss possible origins for this material and place constraints on the orbital parameters and distance of the system.
\n
We present a high-resolution X-ray spectroscopic study of the narrow-line Seyfert 1 galaxy NGC 4051 using two XMM-Newton high-resolution Reflection Grating Spectrometer observations. The spectra reveal three distinct layers of photoionized gas flowing outward from the central black hole: a low-ionization phase (LIP), a higher-ionization phase (HIP), and a high-velocity and high-ionization phase (HVIP). Each absorber leaves characteristic imprints on the soft X-ray spectrum. While the LIP and HVIP are fully consistent with being in ionization equilibrium with the central radiation field over the course of the ∼250 ks spanned by the two observations, the HIP shows a significant change in ionization (3.8σ), suggesting nonequilibrium. By modeling the two spectra with our time-dependent photoionization code ( TEPID ), we constrain the density of the HIP gas to log nH = 7.7_(−0.9)^(+0.2) and estimate its distance to be about R = 0.45_(−0.09)^(+0.80) lt-day from the black hole, corresponding to R = 4000(−800)^(+7000) gravitational radii. In contrast, the narrow soft X-ray emission lines remain constant, consistent with an origin in the more extended narrow-line region. Our results show the value of combining high-resolution and time-resolved spectroscopy to probe the structure, physical conditions, and variability of active galactic nucleus outflows.
",
"doi": "10.3847/1538-4357/ae1614",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-12-10",
"series_number": "1",
"volume": "995",
"issue": "1",
"pages": "6"
},
{
"id": "authors:1xg64-aza16",
"collection": "authors",
"collection_id": "1xg64-aza16",
"cite_using_url": "https://authors.library.caltech.edu/records/1xg64-aza16",
"type": "article",
"title": "The WISSH quasar project. XII. X-ray view of the most luminous quasi-stellar objects at Cosmic Noon",
"author": [
{
"family_name": "Degli Agosti",
"given_name": "C.",
"orcid": "0009-0003-6383-4950"
},
{
"family_name": "Vignali",
"given_name": "C.",
"orcid": "0000-0002-8853-9611"
},
{
"family_name": "Piconcelli",
"given_name": "E.",
"orcid": "0000-0001-9095-2782"
},
{
"family_name": "Zappacosta",
"given_name": "L."
},
{
"family_name": "Bertola",
"given_name": "E.",
"orcid": "0000-0001-5487-2830"
},
{
"family_name": "Middei",
"given_name": "R."
},
{
"family_name": "Saccheo",
"given_name": "I.",
"orcid": "0000-0003-1174-6978"
},
{
"family_name": "Vietri",
"given_name": "G.",
"orcid": "0000-0001-9155-8875"
},
{
"family_name": "Vito",
"given_name": "F."
},
{
"family_name": "Bongiorno",
"given_name": "A."
},
{
"family_name": "Bischetti",
"given_name": "M."
},
{
"family_name": "Bruni",
"given_name": "G.",
"orcid": "0000-0002-5182-6289"
},
{
"family_name": "Carniani",
"given_name": "S."
},
{
"family_name": "Cresci",
"given_name": "G."
},
{
"family_name": "Feruglio",
"given_name": "C.",
"orcid": "0000-0002-4227-6035"
},
{
"family_name": "Salvestrini",
"given_name": "F.",
"orcid": "0000-0003-4751-7421"
},
{
"family_name": "Travascio",
"given_name": "A."
},
{
"family_name": "Gaspari",
"given_name": "M.",
"orcid": "0000-0003-2754-9258"
},
{
"family_name": "Glikman",
"given_name": "E.",
"orcid": "0000-0003-0489-3750"
},
{
"family_name": "Kammoun",
"given_name": "E.",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Lanzuisi",
"given_name": "G.",
"orcid": "0000-0001-9094-0984"
},
{
"family_name": "Laurenti",
"given_name": "M.",
"orcid": "0000-0001-5762-6360"
},
{
"family_name": "Miniutti",
"given_name": "G.",
"orcid": "0000-0003-0707-4531"
},
{
"family_name": "Pinto",
"given_name": "C.",
"orcid": "0000-0003-2532-7379"
},
{
"family_name": "Testa",
"given_name": "V.",
"orcid": "0000-0003-1033-1340"
},
{
"family_name": "Tombesi",
"given_name": "F.",
"orcid": "0000-0002-6562-8654"
},
{
"family_name": "Tortosa",
"given_name": "A.",
"orcid": "0000-0003-3450-6483"
},
{
"family_name": "Fiore",
"given_name": "F.",
"orcid": "0000-0002-4031-4157"
}
],
"abstract": "Aims. To improve our knowledge of the nuclear emission of luminous quasi-stellar objects (QSOs) at Cosmic Noon, we studied the X-ray emission of the WISE/SDSS-selected hyper-luminous (WISSH) QSO sample. It consists of 85 broad-line active galactic nuclei (AGN) with bolometric luminosities Lbol\u2004>\u2004few\u2005×\u20051047 erg s−1 at z\u2004≈\u20042\u2005−\u20054. Our goal is to characterise their X-ray spectral properties and investigate the relation between the X-ray luminosity and the energy output in other bands. To this end, we compared the nuclear properties of powerful QSOs with those derived for the majority of the AGN population.
\nMethods. We were able to perform X-ray spectral analysis for about one-half of the sample. For 16 sources, we applied the hardness ratio analysis, while for the remaining sources we estimated their 2\u2005−\u200510 keV intrinsic luminosity L2\u2005−\u200510; only 8 sources were not detected.
\nResults. We report a large dispersion in L2\u2005−\u200510 despite the narrow distribution in Lbol, 2500 Å intrinsic luminosity L2500\u2004Å, and 6\u2006μm intrinsic luminosity λL6\u2006μm of WISSH QSOs (approximately one-third of the sources classified as X-ray-weak QSOs). This suggests that the properties of the X-ray corona and inner accretion flow in hyper-luminous QSOs can be significantly different from those of typical less powerful AGN. The distribution of the X-ray spectral index does not differ from that of AGN at lower redshift and lower Lbol, and does not depend on the Eddington ratio (λEdd) and X-ray weakness. The majority of WISSH QSOs, for which it was possible to estimate the presence of intrinsic absorption (≈65% of the sample), exhibit little to no obscuration (i.e. column density NH\u2004≤\u20045\u2005×\u20051022 cm−2). Among the X-ray obscured sources, we find some blue QSOs without broad absorption lines (BALs) that fall within the ‘forbidden region’ of the Log(NH)−Log(λEdd) plane, which is typically occupied by dust-reddened QSOs and is associated with intense feedback processes. Additionally, we confirm a significant correlation between L2\u2005−\u200510 and velocity shift of the CIV emission line, a tracer of nuclear ionised outflows.
\nConclusions. Multi-wavelength observations of the broad-line WISSH quasars at Cosmic Noon and, in particular, their complete X-ray coverage, allow us to properly investigate the accretion disk–corona interplay to the highest luminosity regime. The distribution of bolometric corrections kbol and X-ray–to–optical indices αOX of the WISSH quasars is strikingly broad, suggesting that caution should be exercised when using Lbol, L2500\u2004Å, and λL6\u2006μm to estimate the X-ray emission of individual luminous QSOs.
",
"doi": "10.1051/0004-6361/202554943",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2025-10",
"volume": "702",
"pages": "A114"
},
{
"id": "authors:35w12-8p626",
"collection": "authors",
"collection_id": "35w12-8p626",
"cite_using_url": "https://authors.library.caltech.edu/records/35w12-8p626",
"type": "article",
"title": "Explaining the UV to X-ray correlation in active galactic nuclei within the framework of X-ray illumination of accretion discs",
"author": [
{
"family_name": "Kammoun",
"given_name": "E.",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Papadakis",
"given_name": "I. E.",
"orcid": "0000-0001-6264-140X"
},
{
"family_name": "Dov\u010diak",
"given_name": "M.",
"orcid": "0000-0003-0079-1239"
},
{
"family_name": "Lusso",
"given_name": "E.",
"orcid": "0000-0003-0083-1157"
},
{
"family_name": "Nardini",
"given_name": "E.",
"orcid": "0000-0001-9226-8992"
},
{
"family_name": "Risaliti",
"given_name": "G.",
"orcid": "0000-0002-3556-977X"
}
],
"abstract": "Context. It is established that the ultraviolet (UV) and X-ray emission in active galactic nuclei (AGN) is tightly correlated. This correlation is observed both in low- and high-redshift sources. In particular, observations of large samples of quasars revealed a non-linear correlation between UV and X-rays. The physical origin of this correlation is poorly understood.
\nAims. We explore this observed correlation in the framework of the X-ray illumination of the accretion disc by a central source. We showed previously that this model successfully explains the continuum UV/optical time delays, variability, and the broadband spectral energy distribution in AGN.
\nMethods. We used this model to produce 150 000 model spectral energy distributions, assuming a uniform distribution of the model parameters. We computed the corresponding UV (2500 Å) and X-ray (2 keV) monochromatic luminosities and selected only the model data points that agreed with the observed UV-to-X-ray correlation.
\nResults. Our results show that the X-ray illuminated accretion disc model can reproduce the observed correlation for a subset of model configurations with a non-uniform distribution of the black hole mass (MBH), accretion rate (\u1e41/\u1e41Edd), and power transferred from the accretion disc to the corona (Ltransf/Ldisc). In addition, our results reveal a correlation between MBH and \u1e41/\u1e41Edd and between \u1e41/\u1e41Edd and Ltransf/Ldisc that explains the observed X-ray-UV correlation. We also present evidence based on observed luminosities that supports our findings. We finally discuss the implications of our results.
",
"doi": "10.1051/0004-6361/202452629",
"issn": "0004-6361",
"publisher": "EDP Sciences",
"publication": "Astronomy and Astrophysics",
"publication_date": "2025-05",
"volume": "697",
"pages": "A55"
},
{
"id": "authors:e1jmm-rjn72",
"collection": "authors",
"collection_id": "e1jmm-rjn72",
"cite_using_url": "https://authors.library.caltech.edu/records/e1jmm-rjn72",
"type": "article",
"title": "Frequency-resolved Time Lags due to X-Ray Disk Reprocessing in AGN",
"author": [
{
"family_name": "Panagiotou",
"given_name": "Christos",
"orcid": "0009-0001-9034-6261"
},
{
"family_name": "Papadakis",
"given_name": "Iossif",
"orcid": "0000-0001-6264-140X"
},
{
"family_name": "Kara",
"given_name": "Erin",
"orcid": "0000-0003-0172-0854"
},
{
"family_name": "Papoutsis",
"given_name": "Marios"
},
{
"family_name": "Cackett",
"given_name": "Edward M.",
"orcid": "0000-0002-8294-9281"
},
{
"family_name": "Dov\u010diak",
"given_name": "Michal",
"orcid": "0000-0003-0079-1239"
},
{
"family_name": "Garc\u00eda",
"given_name": "Javier A.",
"orcid": "0000-0003-3828-2448",
"clpid": "Garc\u00eda-Javier-A"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Lewin",
"given_name": "Collin",
"orcid": "0000-0002-8671-1190"
}
],
"abstract": "Over the last years, a number of broadband reverberation mapping campaigns have been conducted to explore the short-term UV and optical variability of nearby AGN. Despite the extensive data collected, the origin of the observed variability is still debated in the literature. Frequency-resolved time lags offer a promising approach to distinguish between different scenarios as they probe variability on different timescales. In this study, we present the expected frequency-resolved lags resulting from X-ray reprocessing in the accretion disk. The predicted lags are found to feature a general shape that resembles that of observational measurements while exhibiting strong dependence on various physical parameters. Additionally, we compare our model predictions to observational data for the case of NGC 5548, concluding that the X-ray illumination of the disk can effectively account for the observed frequency-resolved lags and power spectra in a self-consistent way. To date, X-ray disk reprocessing is the only physical model that has successfully reproduced the observed multiwavelength variability, in both amplitude and time delays, across a range of temporal frequencies.
",
"doi": "10.3847/1538-4357/adbf95",
"issn": "0004-637X",
"publisher": "American Astronomical Society",
"publication": "Astrophysical Journal",
"publication_date": "2025-04-20",
"series_number": "2",
"volume": "983",
"issue": "2",
"pages": "132"
},
{
"id": "authors:h2012-2en81",
"collection": "authors",
"collection_id": "h2012-2en81",
"cite_using_url": "https://authors.library.caltech.edu/records/h2012-2en81",
"type": "article",
"title": "NuSTAR Observations of Candidate Subparsec Binary Supermassive Black Holes",
"author": [
{
"family_name": "Saade",
"given_name": "M. Lynne",
"orcid": "0000-0001-7163-7015",
"clpid": "Saade-M-Lynne"
},
{
"family_name": "Brightman",
"given_name": "Murray",
"orcid": "0000-0002-8147-2602",
"clpid": "Brightman-Murray"
},
{
"family_name": "Stern",
"given_name": "Daniel",
"orcid": "0000-0003-2686-9241",
"clpid": "Stern-D"
},
{
"family_name": "Connor",
"given_name": "Thomas",
"orcid": "0000-0002-7898-7664",
"clpid": "Connor-Thomas"
},
{
"family_name": "Djorgovski",
"given_name": "S. G.",
"orcid": "0000-0002-0603-3087",
"clpid": "Djorgovski-S-G"
},
{
"family_name": "D'Orazio",
"given_name": "Daniel J.",
"orcid": "0000-0002-1271-6247",
"clpid": "D'Orazio-Daniel-J"
},
{
"family_name": "Ford",
"given_name": "K. E. S.",
"orcid": "0000-0002-5956-851X",
"clpid": "Foord-K-E-Saavik"
},
{
"family_name": "Graham",
"given_name": "Matthew J.",
"orcid": "0000-0002-3168-0139",
"clpid": "Graham-M-J"
},
{
"family_name": "Haiman",
"given_name": "Zolt\u00e1n",
"orcid": "0000-0003-3633-5403",
"clpid": "Haiman-Zolt\u00e1n"
},
{
"family_name": "Jun",
"given_name": "Hyunsung D.",
"orcid": "0000-0003-1470-5901",
"clpid": "Jun-Hyunsung-D"
},
{
"family_name": "Kammoun",
"given_name": "Elias",
"orcid": "0000-0002-0273-218X",
"clpid": "Kammoun-Elias"
},
{
"family_name": "Kraft",
"given_name": "Ralph P.",
"orcid": "0000-0002-0765-0511",
"clpid": "Kraft-Ralph-P"
},
{
"family_name": "McKernan",
"given_name": "Barry",
"orcid": "0000-0002-9726-0508",
"clpid": "McKernan-Barry"
},
{
"family_name": "Vikhlinin",
"given_name": "Alexei",
"orcid": "0000-0001-8121-0234",
"clpid": "Vikhlinin-Alexei"
},
{
"family_name": "Walton",
"given_name": "Dominic J.",
"orcid": "0000-0001-5819-3552",
"clpid": "Walton-Dominic-J"
}
],
"abstract": "\n
We present an analysis of NuSTAR X-ray observations of three active galactic nuclei (AGN) that were identified as candidate subparsec binary supermassive black hole (SMBH) systems in the Catalina Real-Time Transient Survey based on apparent periodicity in their optical light curves. Simulations predict that close-separation accreting SMBH binaries will have different X-ray spectra than single accreting SMBHs. We previously observed these AGN with Chandra and found no differences between their low-energy X-ray properties and the larger AGN population. However, some models predict differences to be more prominent at energies higher than probed by Chandra. We find that even at the higher energies probed by NuSTAR, the spectra of these AGN are indistinguishable from the larger AGN population. This could rule out models predicting large differences in the X-ray spectra in the NuSTAR bands. Alternatively, it might mean that these three AGN are not binary SMBHs.
\n