scholarly journals Black-hole spin dependence in the light curves of tidal disruption events

2012 ◽  
Vol 86 (6) ◽  
Author(s):  
Michael Kesden
Keyword(s):  
Black Hole ◽  
Light Curves ◽  
Spin Dependence ◽  
Tidal Disruption ◽  
Black Hole Spin

scholarly journals Near-Eddington Luminosity Flares from Quiescent Supermassive Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 319-324
Author(s):  
Suvi Gezari
Keyword(s):  
Black Hole ◽  
Thermal Emission ◽  
Rare Event ◽  
Light Curves ◽  
Spectral Energy ◽  
Wide Field ◽  
Tidal Disruption ◽  
X Ray ◽  
Solar Type ◽  
Detection Capabilities

AbstractA dormant supermassive black hole lurking in the center of a galaxy will be revealed when a star passes within its tidal disruption radius, is disrupted, and a flare of electromagnetic radiation is emitted when the bound stellar debris is accreted. Although the tidal disruption of a star is a rare event in a galaxy, ~ 10−4 yr−1, observational candidates have emerged in all-sky X-ray and deep UV surveys in the form of luminous UV/X-ray flares from otherwise quiescent galaxies. We present the light curves and broadband properties of three tidal disruption candidates discovered in the UV by GALEX, and find that (1) the light curves are well-fitted by the power-law decline expected for the fallback of debris from a tidally disrupted solar-type star, and (2) the UV/optical spectral energy distributions can be attributed to thermal emission from an envelope of debris located at ten times the tidal disruption radius of the central black hole. We use the observed peak absolute optical magnitudes of the flares to predict the detection capabilities of the next generation of wide-field optical synoptic surveys.

scholarly journals ASASSN-15lh: a TDE about a maximally rotating 109 M⊙ black hole

2020 ◽  
Vol 497 (1) ◽  
pp. L13-L18 ◽  
Author(s):  
Andrew Mummery ◽  
Steven A Balbus
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Light Curves ◽  
The Novel ◽  
Black Hole Mass ◽  
Tidal Disruption ◽  
Scaling Relationships ◽  
Best Fitting ◽  
Infrared Frequencies ◽  
Disruption Event

ABSTRACT We model the light curves of the novel and extremely luminous transient ASASSN-15lh at nine different frequencies, from infrared to ultraviolet photon energies, as an evolving relativistic disc produced in the aftermath of a tidal disruption event (TDE). Good fits to all nine light curves are simultaneously obtained when Macc ≃ 0.07 M⊙ is accreted on to a black hole of mass M ≃ 109 M⊙ and near-maximal rotation a/rg = 0.99. The best-fitting black hole mass is consistent with a number of existing estimates from galactic scaling relationships. If confirmed, our results represent the detection of one of the most massive rapidly spinning black holes to date, and are strong evidence for a TDE origin for ASASSN-15lh. This would be the first TDE to be observed in the disc-dominated state at optical and infrared frequencies.

scholarly journals Extreme variability in an active galactic nucleus: Gaia16aax

2020 ◽  
Vol 493 (1) ◽  
pp. 477-495 ◽  
Author(s):  
G Cannizzaro ◽  
M Fraser ◽  
P G Jonker ◽  
J E Pringle ◽  
S Mattila ◽  
...  
Keyword(s):  
Black Hole ◽  
Selection Criteria ◽  
Light Curves ◽  
Tidal Disruption ◽  
Transient Event ◽  
Balmer Lines ◽  
Extreme Variability ◽  
Event Variable ◽  
Dust Absorption

ABSTRACT We present the results of a multiwavelength follow-up campaign for the luminous nuclear transient Gaia16aax, which was first identified in 2016 January. The transient is spatially consistent with the nucleus of an active galaxy at z = 0.25, hosting a black hole of mass ${\sim }6\times 10^8\, \mathrm{M}_\odot$. The nucleus brightened by more than 1 mag in the Gaia G band over a time-scale of less than 1 yr, before fading back to its pre-outburst state over the following 3 yr. The optical spectra of the source show broad Balmer lines similar to the ones present in a pre-outburst spectrum. During the outburst, the H α and H β emission lines develop a secondary peak. We also report on the discovery of two transients with similar light-curve evolution and spectra: Gaia16aka and Gaia16ajq. We consider possible scenarios to explain the observed outbursts. We exclude that the transient event could be caused by a microlensing event, variable dust absorption or a tidal encounter between a neutron star and a stellar mass black hole in the accretion disc. We consider variability in the accretion flow in the inner part of the disc, or a tidal disruption event of a star ${\ge } 1 \, \mathrm{M}_{\odot }$ by a rapidly spinning supermassive black hole as the most plausible scenarios. We note that the similarity between the light curves of the three Gaia transients may be a function of the Gaia alerts selection criteria.

scholarly journals Black hole spin dependence of general relativistic multi-transonic accretion close to the horizon

New Astronomy ◽  
2015 ◽  
Vol 37 ◽  
pp. 81-104 ◽  
Author(s):  
Tapas K. Das ◽  
Sankhasubhra Nag ◽  
Swathi Hegde ◽  
Sourav Bhattacharya ◽  
Ishita Maity ◽  
...  
Keyword(s):  
Black Hole ◽  
Spin Dependence ◽  
Black Hole Spin ◽  
General Relativistic

scholarly journals A minimal timescale for the continuum in 4U 1608-52 and Aql X-1

2021 ◽  
Vol 502 (1) ◽  
pp. L72-L78
Author(s):  
K Mohamed ◽  
E Sonbas ◽  
K S Dhuga ◽  
E Göğüş ◽  
A Tuncer ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Power Spectra ◽  
Light Curves ◽  
State Transitions ◽  
Strong Positive Correlation ◽  
Present Evidence ◽  
X Ray ◽  
X Ray Binaries ◽  
The Continuum

ABSTRACT Similar to black hole X-ray binary transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries. Using a method based on wavelets and light curves constructed from archival Rossi X-ray Timing Explorer observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.

scholarly journals Influence of the geometric configuration of accretion flow on the black hole spin dependence of relativistic acoustic geometry

2018 ◽  
Vol 27 (03) ◽  
pp. 1850023 ◽  
Author(s):  
Pratik Tarafdar ◽  
Tapas K. Das
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Geometric Configuration ◽  
Surface Gravity ◽  
Linear Perturbation ◽  
Flow Profile ◽  
White Hole ◽  
Accretion Flow ◽  
Black Hole Spin ◽  
General Relativistic

Linear perturbation of general relativistic accretion of low angular momentum hydrodynamic fluid onto a Kerr black hole leads to the formation of curved acoustic geometry embedded within the background flow. Characteristic features of such sonic geometry depend on the black hole spin. Such dependence can be probed by studying the correlation of the acoustic surface gravity [Formula: see text] with the Kerr parameter [Formula: see text]. The [Formula: see text]–[Formula: see text] relationship further gets influenced by the geometric configuration of the accretion flow structure. In this work, such influence has been studied for multitransonic shocked accretion where linear perturbation of general relativistic flow profile leads to the formation of two analogue black hole-type horizons formed at the sonic points and one analogue white hole-type horizon which is formed at the shock location producing divergent acoustic surface gravity. Dependence of the [Formula: see text]–[Formula: see text] relationship on the geometric configuration has also been studied for monotransonic accretion, over the entire span of the Kerr parameter including retrograde flow. For accreting astrophysical black holes, the present work thus investigates how the salient features of the embedded relativistic sonic geometry may be determined not only by the background spacetime, but also by the flow configuration of the embedding matter.

scholarly journals Spectral and polarization properties of black hole accretion disc emission: including absorption effects

2020 ◽  
Author(s):  
R Taverna ◽  
L Marra ◽  
S Bianchi ◽  
M Dovčiak ◽  
R Goosmann ◽  
...  
Keyword(s):  
Black Hole ◽  
Polarization State ◽  
General Rule ◽  
Accretion Disc ◽  
Accretion Discs ◽  
Polarization Degree ◽  
Monte Carlo Code ◽  
Black Hole Spin ◽  
Black Hole Accretion ◽  
Hole Accretion

Abstract The study of radiation emitted from black hole accretion discs represents a crucial way to understand the main physical properties of these sources, and in particular the black hole spin. Beside spectral analysis, polarimetry is becoming more and more important, motivated by the development of new techniques which will soon allow to perform measurements also in the X- and γ-rays. Photons emitted from black hole accretion discs in the soft state are indeed expected to be polarized, with an energy dependence which can provide an estimate of the black hole spin. Calculations performed so far, however, considered scattering as the only process to determine the polarization state of the emitted radiation, implicitly assuming that the temperatures involved are such that material in the disc is entirely ionized. In this work we generalize the problem by calculating the ionization structure of a surface layer of the disc with the public code cloudy, and then by determining the polarization properties of the emerging radiation using the Monte Carlo code stokes. This allows us to account for absorption effects alongside scattering ones. We show that including absorption can deeply modify the polarization properties of the emerging radiation with respect to what is obtained in the pure-scattering limit. As a general rule, we find that the polarization degree is larger when absorption is more important, which occurs e.g. for low accretion rates and/or spins when the ionization of the matter in the innermost accretion disc regions is far from complete.

scholarly journals NuSTAR OBSERVATIONS OF THE BLACK HOLE GS 1354–645: EVIDENCE OF RAPID BLACK HOLE SPIN

2016 ◽  
Vol 826 (1) ◽  
pp. L12 ◽  
Author(s):  
A. M. El-Batal ◽  
J. M. Miller ◽  
M. T. Reynolds ◽  
S. E. Boggs ◽  
F. E. Chistensen ◽  
...  
Keyword(s):  
Black Hole ◽  
Black Hole Spin
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