scholarly journals AT 2018lqh: Black Hole Born from a Rotating Star?

2021 ◽  
Vol 922 (2) ◽  
pp. L34
Author(s):  
Daichi Tsuna ◽  
Kazumi Kashiyama ◽  
Toshikazu Shigeyama
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Late Time ◽  
High Luminosity ◽  
X Ray ◽  
Uv Emission ◽  
Upper Limits ◽  
Rotating Star

Abstract Recently an intriguing transient, AT 2018lqh, with only a day-scale duration and a high luminosity of 7 × 1042 erg s−1, was discovered. While several possibilities are raised on its origin, the nature of this transient is yet to be unveiled. We propose that a black hole (BH) with ∼30 M ⊙ forming from a rotating blue supergiant can generate a transient like AT 2018lqh. We find that this scenario can consistently explain the optical/UV emission and the tentative late-time X-ray detection, as well as the radio upper limits. If super-Eddington accretion onto the nascent BH powers the X-ray emission, continued X-ray observations may be able to test the presence of an accretion disk around the BH.

scholarly journals Observational properties of relativistic black hole winds

2006 ◽  
Vol 2 (S238) ◽  
pp. 471-472
Author(s):  
Ken-ya Watarai
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
High Luminosity ◽  
Disk Thickness ◽  
X Ray ◽  
Mass Outflow ◽  
Wind Velocities

AbstractWe examine observational properties of relativistic black hole winds as an origin of high luminosity sources such as microquasars and ultra-luminous X-ray sources (ULXs). When strong relativistic wind/outflow happens in the vicinity of the black hole, the wind might form the optically-thick photosphere. Therefore the emission observed in ULXs might come from the photosphere of the wind, not from the accretion disk.We found that the location of the photosphere is larger than the disk thickness for super-Eddington mass-outflow rates and sub-relativistic wind velocities (v ∼ 0.1–0.2 c). To understand the radiative structure in the high luminosity sources, we should take into account not only the emission from the accretion disk but also the emission from the outflow at the same time.

scholarly journals Rapid late-time X-ray brightening of the tidal disruption event OGLE16aaa

2020 ◽  
Vol 639 ◽  
pp. A100 ◽  
Author(s):  
Jari J. E. Kajava ◽  
Margherita Giustini ◽  
Richard D. Saxton ◽  
Giovanni Miniutti
Keyword(s):  
Black Hole ◽  
Host Galaxy ◽  
Late Time ◽  
Tidal Disruption ◽  
Massive Black Hole ◽  
X Ray ◽  
Tidal Forces ◽  
Upper Limits ◽  
Optical Light Curve ◽  
Disruption Event

Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces. OGLE16aaa is one such tidal disruption event (TDE) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year. OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9, 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak. Between June 16–21, 2016, Swift/XRT also detected OGLE16aaa and based on the stacked spectrum, we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week. No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one. A further XMM-Newton observation on November 30, 2016 showed that almost a year after the optical/UV peak, the X-ray emission was still at an elevated level, while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy. In all X-ray observations, the spectra were nicely modeled with a 50–70 eV thermal component with no intrinsic absorption, with a weak X-ray tail seen only in the November 30 XMM-Newton observation. The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh. We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to 182 ± 5 days, which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion. Alternatively, the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months.

scholarly journals Dynamical Evolution of Accretion Flow onto a Black Hole

1998 ◽  
Vol 188 ◽  
pp. 455-456
Author(s):  
M. Yokosawa
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Accretion Disk ◽  
Dynamical Evolution ◽  
Galactic Nuclei ◽  
Thick Disk ◽  
X Ray ◽  
General Relativistic ◽  
Inner Region

Active galactic nuclei(AGN) produce many type of active phenomena, powerful X-ray emission, UV hump, narrow beam ejection, gamma-ray emission. Energy of these phenomena is thought to be brought out binding energy between a black hole and surrounding matter. What condition around a black hole produces many type of active phenomena? We investigated dynamical evolution of accretion flow onto a black hole by using a general-relativistic, hydrodynamic code which contains a viscosity based on the alpha-model. We find three types of flow's pattern, depending on thickness of accretion disk. In a case of the thin disk with a thickness less than the radius of the event horizon at the vicinity of a marginally stable orbit, the accreting flow through a surface of the marginally stable orbit becomes thinner due to additional cooling caused by a general-relativistic Roche-lobe overflow and horizontal advection of heat. An accretion disk with a middle thickness, 2rh≤h≤ 3rh, divides into two flows: the upper region of the accreting flow expands into the atmosphere of the black hole, and the inner region of the flow becomes thinner, smoothly accreting onto the black hole. The expansion of the flow generates a dynamically violent structure around the event horizon. The kinetic energy of the violent motion becomes equivalent to the thermal energy of the accreting disk. The shock heating due to violent motion produces a thermally driven wind which flows through the atmosphere above the accretion disk. A very thick disk, 4rh≤h,forms a narrow beam whose energy is largely supplied from hot region generated by shock wave. The accretion flowing through the thick disk,h≥ 2rh, cannot only form a single, laminar flow falling into the black hole, but also produces turbulent-like structure above the event horizon. The middle disk may possibly emit the X-ray radiation observed in active galactic nuclei. The thin disk may produce UV hump of Seyfert galaxy. Thick disk may produce a jet observed in radio galaxy. The thickness of the disk is determined by accretion rate, such ashκ κes/cṁf(r) κ 10rhṁf(r), at the inner region of the disk where the radiation pressure dominates over the gas pressure. Here, Ṁ is the accretion rate and ṁ is the normarized one by the critical-mass flux of the Eddington limit. κesandcare the opacity by electron scattering and the velocity of light.f(r) is a function with a value of unity far from the hole.

scholarly journals Warm and thick corona for a magnetically supported disk in galactic black hole binaries

2020 ◽  
Vol 633 ◽  
pp. A35 ◽  
Author(s):  
D. Gronkiewicz ◽  
A. Różańska
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Accretion Disk ◽  
Thermal Instability ◽  
Stellar Mass ◽  
Rotational Instability ◽  
X Ray ◽  
Black Hole Binaries ◽  
Radiative Processes ◽  
Gas Heating

Context. We self-consistently model a magnetically supported accretion disk around a stellar-mass black hole with a warm optically thick corona based on first principles. We consider the gas heating by magneto-rotational instability dynamo. Aims. Our goal is to show that the proper calculation of the gas heating by magnetic dynamo can build up the warm optically thick corona above the accretion disk around a black hole of stellar mass. Methods. Using the vertical model of the disk supported and heated by the magnetic field together with radiative transfer in hydrostatic and radiative equilibrium, we developed a relaxation numerical scheme that allowed us to compute the transition form the disk to corona in a self-consistent way. Results. We demonstrate here that the warm (up to 5 keV) optically thick (up to 10 τes) Compton-cooled corona can form as a result of magnetic heating. A warm corona like this is stronger in the case of the higher accretion rate and the greater magnetic field strength. The radial extent of the warm corona is limited by local thermal instability, which purely depends on radiative processes. The obtained coronal parameters are in agreement with those constrained from X-ray observations. Conclusions. A warm magnetically supported corona tends to appear in the inner disk regions. It may be responsible for soft X-ray excess seen in accreting sources. For lower accretion rates and weaker magnetic field parameters, thermal instability prevents a warm corona, giving rise to eventual clumpiness or ionized outflow.

scholarly journals The stringent upper limit on jet power in the persistent soft-state source 4U 1957+11

2020 ◽  
Vol 498 (1) ◽  
pp. L40-L45
Author(s):  
Thomas J Maccarone ◽  
Arlo Osler ◽  
James C A Miller-Jones ◽  
P Atri ◽  
David M Russell ◽  
...  
Keyword(s):  
Black Hole ◽  
Type I ◽  
X Ray ◽  
Upper Limit ◽  
Source Distance ◽  
Upper Limits ◽  
Soft State ◽  
Hard State ◽  
Comprehensive Search ◽  
Radio Power

ABSTRACT We present extremely deep upper limits on the radio emission from 4U 1957+11, an X-ray binary that is generally believed to be a persistently accreting black hole that is almost always in the soft state. We discuss a more comprehensive search for Type I bursts than in past work, revealing a stringent upper limit on the burst rate, bolstering the case for a black hole accretor. The lack of detection of this source at the 1.07 μJy/beam noise level indicates jet suppression that is stronger than expected even in the most extreme thin disc models for radio jet production – the radio power here is 1500–3700 times lower than the extrapolation of the hard state radio/X-ray correlation, with the uncertainties depending primarily on the poorly constrained source distance. We also discuss the location and velocity of the source and show that it must have either formed in the halo or with a strong asymmetric natal kick.

scholarly journals Complex optical/UV and X-ray variability in Seyfert 1 galaxy Mrk 509

2021 ◽  
Vol 38 ◽  
Author(s):  
Neeraj Kumari ◽  
Main Pal ◽  
Sachindra Naik ◽  
Arghajit Jana ◽  
Gaurava K. Jaisawal ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Timing Analysis ◽  
Optical Emission ◽  
Light Curves ◽  
Thermal Component ◽  
X Ray ◽  
Uv Emission ◽  
Average Spectrum ◽  
Entire Duration ◽  
Using Data

Abstract We performed a detailed spectral and timing analysis of a Seyfert 1 galaxy Mrk 509 using data from the Neil Gehrels Swift observatory that spanned over $\sim$ 13 years between 2006 and 2019. To study the variability properties from the optical/UV to X-ray emission, we used a total of 275 pointed observations in this work. The average spectrum over the entire duration exhibits a strong soft X-ray excess above the power law continuum. The soft X-ray excess is well described by two thermal components with temperatures of kT $_{\rm BB1}\sim$ 120 eV and kT $_{\rm BB2}\sim$ 460 eV. The warm thermal component is likely due to the presence of an optically thick and warm Comptonizing plasma in the inner accretion disk. The fractional variability amplitude is found to be decreasing with increasing wavelength, i.e., from the soft X-ray to UV/optical emission. However, the hard X-ray (2–8 keV) emission shows very low variability. The strength of the correlation within the UV and the optical bands (0.95–0.99) is found to be stronger than the correlation between the UV/optical and X-ray bands (0.40–0.53). These results clearly suggest that the emitting regions of the X-ray and UV/optical emission are likely distinct or partly interacting. Having removed the slow variations in the light curves, we find that the lag spectrum is well described by the 4/3 rule for the standard Shakura–Sunyaev accretion disk when we omit X-ray lags. All these results suggest that the real disk is complex, and the UV emission is likely reprocessed in the accretion disk to give X-ray and optical emission.

Outbursts of the black hole X-ray transient KV UMa (XTE J1118+480) in the optical band

2020 ◽  
Vol 37 ◽  
Author(s):  
Vojtěch Šimon
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Short Duration ◽  
X Ray ◽  
Viscous Instability ◽  
Slow Decline ◽  
The One ◽  
The Individual ◽  
Double Event

Abstract KV UMa (XTE J1118+480) is an X-ray binary that is known to undergo outbursts in 2000 and 2005. This paper presents the discovery of a large outburst starting in 1927 on the archival photographic plates and an analysis of the long-term optical activity of this system. We used the photographic data from DASCH (Digital Access to a Sky Century @ Harvard). We placed the 1927 outburst in the context of the observed outbursts of KV UMa. We show that it is a double event, with a precursor similar to the one of the outbursts in 2000. We find a big difference between the 1927 and 2000 outbursts as regards the length of the gap between the precursor and the main outburst. It is more than 250 d in 1927, whereas it is about 20 d in 2000, although the brightnesses of all peaks are mutually comparable. We also show that the individual optical outbursts of KV UMa differ from each other by the duration of the stage of a slow decline of brightness (sometimes roughly a plateau). This determines the length of the entire main outburst. Both the peak magnitude and the brightness of the outburst when the slow decline transitions to a steep final decaying branch plausibly reproduce in all three outbursts. In the interpretation, the short duration of the precursor is caused by the fact that only the thermal-viscous instability operated in the accretion disk while also the tidal instability of the disk contributed in the subsequent main outburst.

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