Results 41 to 50 of about 159,631 (288)

Unraveling the enigmatic soft x‐ray excess: Current understanding and future perspectives

Astronomische Nachrichten, Volume 344, Issue 6, August 2023., 2023
Abstract This article explores various theoretical models proposed to explain the soft x‐ray excess phenomenon, including warm Comptonization, ionized reflection models, and ionized outflowing disc winds. The soft x‐ray excess is better understood thanks to crucial observations made by ROSAT, XMM‐Newton, and eROSITA.
Thomas Boller
wiley   +1 more source

Investigation of some galactic and extragalactic gravitational phenomena [PDF]

Serbian Astronomical Journal, 2012
Here we present a short overview of the most important results of our investigations of the following galactic and extragalactic gravitational phenomena: supermassive black holes in centers of galaxies and quasars, supermassive black hole ...
Jovanović P.
doaj   +1 more source

Multiwavelength astrophysics of the blazar OJ 287 and the project MOMO

Astronomische Nachrichten, Volume 344, Issue 4, May 2023., 2023
Abstract We are carrying out the densest and longest multiyear, multiwavelength monitoring project of OJ 287 ever done. The project MOMO (Multiwavelength Observations and Modeling of OJ 287) covers wavelengths from the radio to the high‐energy regime. A few selected observations are simultaneous with those of the Event Horizon Telescope (EHT).
S. Komossa, A. Kraus, D. Grupe, M.L. Parker, A. Gonzalez, L.C. Gallo, M.A. Gurwell, S. Laine, S. Yao, S. Chandra, L. Dey, J.L. Gómez, K. Hada, D. Haggard, A.R. Hollett, H. Jermak, S. Jorstad, T.P. Krichbaum, S. Markoff, C. McCall, J. Neilsen, M. Nowak   +21 more
wiley   +1 more source

Searching for overlooked TDEs in the 4XMM catalogue

Astronomische Nachrichten, Volume 344, Issue 4, May 2023., 2023
Abstract Tidal disruption events (TDEs) are usually discovered as bright transients, either in the X‐ray or optical/UV band. These events are often characterized by a “super‐soft” emission in the X‐ray band, which has not been observed in any other extragalactic source, with few exceptions (novae and supersoft active galactic nuclei, AGN), which can ...
Andrea Sacchi, Guido Risaliti, Giovanni Miniutti   +2 more
wiley   +1 more source

Modeling the Central Supermassive Black Hole Mass of Quasars via the LSTM Approach

The Astrophysical Journal, 2023
One of the fundamental questions about quasars is related to their central supermassive black holes. The reason for the existence of these black holes with such a huge mass is still unclear, and various models have been proposed to explain them. However,
Seyed Sajad Tabasi, Reyhaneh Vojoudi Salmani, Pouriya Khaliliyan, Javad T. Firouzjaee   +3 more
doaj   +1 more source

Winds in ultraluminous X‐ray sources: New challenges

Astronomische Nachrichten, Volume 344, Issue 4, May 2023., 2023
Abstract Ultraluminous X‐ray sources (ULXs) are extreme X‐ray binaries shining above 1039 erg/s, in most cases as a consequence of super‐Eddington accretion onto neutron stars and stellar‐mass black holes accreting above their Eddington limit. This was understood after the discovery of coherent pulsations, cyclotron lines, and powerful winds.
C. Pinto, P. Kosec
wiley   +1 more source

Fourier spectral‐timing techniques for the study of accreting black holes

Astronomische Nachrichten, Volume 344, Issue 4, May 2023., 2023
Abstract The X‐ray signal from active galactic nuclei and black hole (BH) X‐ray binaries is highly variable on a range of timescales. This variability can be exploited to map the region of interest close to the BH, which is far too small to directly image for all but two BHs in the Universe.
Adam Ingram
wiley   +1 more source

Titans of the early Universe: The Prato statement on the origin of the first supermassive black holes [PDF]

Publications Astronomical Society of Australia, 2018
In recent years, the discovery of massive quasars at $z\sim7$ has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early Universe. Mounting observational and theoretical evidence indicates the
T. Woods, B. Agarwal, V. Bromm, A. Bunker, Ke-Jung Chen, Sunmyon Chon, A. Ferrara, S. Glover, L. Haemmerlé, Z. Haiman, T. Hartwig, A. Heger, S. Hirano, T. Hosokawa, K. Inayoshi, R. Klessen, C. Kobayashi, F. Koliopanos, M. Latif, Yue-xing Li, L. Mayer, M. Mezcua, P. Natarajan, F. Pacucci, M. Rees, J. Regan, Y. Sakurai, S. Salvadori, R. Schneider, M. Surace, Takamitsu L. Tanaka, D. Whalen, N. Yoshida   +32 more
semanticscholar   +1 more source

The birth of a supermassive black hole binary [PDF]

Monthly Notices of the Royal Astronomical Society, 2017
12 pages, 12 Figures, submitted to ...
Pfister, Hugo, Lupi, Alessandro, Capelo, Pedro R, Volonteri, Marta, Bellovary, Jillian M, Dotti, Massimo   +5 more
openaire   +3 more sources

Extreme accretion events: TDEs and changing‐look AGN

Astronomische Nachrichten, Volume 344, Issue 4, May 2023., 2023
Abstract We present a review of the topics of X‐ray stellar tidal disruption events (TDEs) and changing‐look active galactic nuclei (AGN). Stars approaching a supermassive black hole (SMBH) can be tidally disrupted and accreted. TDEs were first discovered in the X‐ray regime and appear as luminous, giant‐amplitude flares from inactive galaxies.
S. Komossa, D. Grupe
wiley   +1 more source