We report the discovery of year-scale X-ray variation in the nuclear region of the M87 by reanalyzing the 8 Chandra observations from 2007 to 2008. The X-ray spectra are fitted and decomposed into the disk and flaring components. This year-scale X-ray variability can be explained quite well by a simple clumpy accretion model. We conclude that the central super-massive black hole of the M87 was accreting a cloud of $\sim0.5$M$_\odot$ at that time.
Binary black hole (BBH) mergers, particularly those with component masses in the pair-instability gap, may be produced by hierarchical mergers in the disks surrounding Active Galactic Nuclei (AGN). While the interaction of an embedded BBH with an AGN disk is typically assumed to facilitate a merger, recent high-resolution hydrodynamical simulations challenge this assumption. However, these simulations often have simplified treatments for the gas thermodynamics. In this work, we model the possible consequence of various feedback from an embedded BBH with a simple model that maintains an enhance…
Active galactic nuclei (AGN) are powered by the accretion of disks of gas onto supermassive black holes (SMBHs). Stars and stellar remnants orbiting the SMBH in the nuclear star cluster (NSC) will interact with the AGN disk. Orbiters plunging through the disk experience a drag force and, through repeated passage, can have their orbits captured by the disk. A population of embedded objects in AGN disks may be a significant source of binary black hole mergers, supernovae, tidal disruption events and embedded gamma-ray bursts. For two representative AGN disk models we use geometric drag and Bondi…
Migration Traps as Variability Attractors. I. Optical/UV Signatures of Embedded Stellar-Mass Black Holes in Active Galactic Nucleus Disks
Xiamen University（厦门大学）；SHAO-XMU Joint Center for Astrophysics, Xiamen University（厦大-上海天文台联合天体物理中心）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；University of Science and Technology of China（中国科学技术大学）；Guangxi University（广西大学）
White dwarfs (WDs) embedded in gaseous disks of active galactic nucleus (AGNs) can rapidly accrete materials from the disks and grow in mass to reach or even exceed the Chandrasekhar limit. Binary WD (BWD) mergers are also believed to occur in AGN accretion disks. We study observational signatures from these events. We suggest that mass-accreting WDs and BWD mergers in AGN disks can lead to thermonuclear explosions that drive an ejecta shock breakout from the disk surface and power a slow-rising, relatively dim Type Ia supernova (SN). Such SNe Ia may be always outshone by the emission of the A…
We perform a series of high-resolution 2D hydrodynamical simulations of equal-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) accretion disks to study whether these binaries can be driven to merger by the surrounding gas. We find that the gravitational softening adopted for the BBH has a profound impact on this result. When the softening is less than ten percent of the binary separation, we show that, in agreement with recent simulations of isolated equal-mass binaries, prograde BBHs expand in time rather than contract. Eventually, however, the binary separation become…
Quasi-periodic Eruptions from Recurrent Satellite Black Hole Transits through Magnetized Galactic Nucleus Accretion Disks
Xiamen University（厦门大学）；SHAO-XMU Joint Center for Astrophysics, Xiamen University（厦大-上海天文台天体物理联合中心）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）
A precessing jet from an active galactic nucleus drives gas outflow from a disk galaxy
University of California Irvine（加州大学尔湾分校）；California Institute of Technology（加州理工学院）；National Radio Astronomy Observatory（美国国家射电天文台）；University of Virginia（弗吉尼亚大学）；University of Arizona（亚利桑那大学）；European Southern Observatory（欧洲南方天文台）；Joint Atacama Large Millimeter Array Observatory（阿塔卡马大型毫米波/亚毫米波阵列联合观测站）；University of California Riverside（加州大学河滨分校）；University of Florida（佛罗里达大学）；Foundation for Research and Technology -Hellas（希腊研究与技术基金会）；European University Cyprus（塞浦路斯欧洲大学）；Flatiron Institute（平顿研究所）；University of California, Los Angeles（加州大学洛杉矶分校）；W. M. Keck Observatory（韦克天文台）；Carnegie Institution for Science（卡内基科学机构）；University of Toledo（托莱多大学）；Occidental College（西方学院）；University of California Santa Cruz（加州大学圣克鲁兹分校）；NPC Worldwide, LLC（NPC环球有限公司）；University of Crete（克里特大学）；Australian National University（澳大利亚国立大学）；Australian Research Council Centre of Excellence for All Sky Astrophysics in Three Dimensions（澳大利亚研究理事会三维全天空天体物理学卓越中心）；Hiroshima University（广岛大学）；Space Telescope Science Institute（太空望远镜科学研究所）；Cahill Center for Astronomy and Astrophysics（凯尔天文学与天体物理学中心）；University of Hawaii at Manoa（夏威夷大学马诺阿分校）
A Two-zone Accretion Disk in the Changing-look Active Galactic Nucleus 1ES 1927+654: Physical Implications for Tidal Disruption Events and Super-Eddington Accretion
We present Multi-Unit Spectroscopic Explorer (MUSE) integral-field spectroscopy of ESO 253$-$G003, which hosts a known Active Galactic Nucleus (AGN) and the periodic nuclear transient ASASSN-14ko, observed as part of the All-weather MUse Supernova Integral-field of Nearby Galaxies (AMUSING) survey. The MUSE observations reveal that the inner region hosts two AGN separated by $1.4\pm0.1~\rm{kpc}$ ($\approx 1.\!\!^{\prime\prime}7$). The brighter nucleus has asymmetric broad, permitted emission-line profiles and is associated with the archival AGN designation. The fainter nucleus does not have a …
There is a broad consensus that accretion onto supermassive black holes and consequent jet formation power the observed emission from active galactic nuclei (AGNs). However, there has been less agreement about how jets form in accretion flows, their possible relationship to black hole spin, and how they interact with the surrounding medium. There have also been theoretical concerns about instabilities in standard accretion disk models and lingering discrepancies with observational constraints. Despite seemingly successful applications to X-ray binaries, the standard accretion disk model faces …
We present the rest-frame optical morphologies of active galactic nucleus (AGN) host galaxies at 1.5<z<3, using near-infrared imaging from the Hubble Space Telescope Wide Field Camera 3, the first such study of AGN host galaxies at these redshifts. The AGN are X-ray selected from the Chandra Deep Field South and have typical luminosities of 1E42 < L_X < 1E44 erg/s. Accreting black holes in this luminosity and redshift range account for a substantial fraction of the total space density and black hole mass growth over cosmic time; they thus represent an important mode of black hole growth in the…
LVK S241125n: Massive Binary Black Hole Merger Produces Gamma Ray Burst in Active Galactic Nucleus Disk
University of Science and Technology of China（中国科学技术大学）；Università degli Studi di Ferrara（费拉拉大学）；ICRANet（国际相对论天体物理中心网络）；Sapienza Università di Roma（罗马大学）；INAF – Osservatorio Astronomico d’Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）；Shanghai Astronomical Observatory（上海天文台）；Ningbo University（宁波大学）
We report short-cadence monitoring of a radio-quiet Active Galactic Nuclei (AGN), NGC7469, at 95 GHz (3 mm) over a period of 70 days with the CARMA telescope. The AGN varies significantly ($\pm3σ$ from the mean) by a factor of two within 4-5 days. The intrinsic 95 GHz variability amplitude in excess of the measurement noise (10%) and relative to the mean flux is comparable to that in the X-rays, and much higher than at 8.4 GHz. The mm-band variability and its similarity to the X-ray variability adds to the evidence that the mm and X-ray emission have the same physical origin, and are associate…
Interpreting Swift and NuSTAR Observations of the Low-Luminosity Active Galactic Nucleus NGC 4278 with Radiatively Inefficient Accretion Flows and Implications for Neutrino Emission
The Pennsylvania State University（宾夕法尼亚州立大学）；University of Utah（犹他大学）；Tohoku University（东北大学）
We present results from a new optical/UV/X-ray monitoring campaign of the luminous Seyfert galaxy Fairall 9 using the Swift satellite. Using the UV-Optical Telescope (UVOT) on Swift, we find correlated optical/UV variability on all time scales ranging from the sampling time (4-days) to the length of the campaign (2.5 months). In one noteworthy event, the UW2-band flux dips by 20% in 4-days, and then recovers equally quickly; this event is not seen in either the optical or the X-ray bands. We argue that this event provides further evidence that a significant fraction of the UV-emission must be …
Active Galactic Nucleus Tori: Potential Birthplace to Millions of Planets
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（波兰科学院尼古拉·哥白尼天文学中心）；New Mexico State University（新墨西哥州立大学）；CUNY Borough of Manhattan Community College（纽约市立大学曼哈顿社区学院）；American Museum of Natural History（美国自然历史博物馆）
