scholarly journals The soft state of the black hole transient source MAXI J1820+070: emission from the edge of the plunge region?

2020 ◽  
Vol 493 (4) ◽  
pp. 5389-5396 ◽  
Author(s):  
A C Fabian ◽  
D J Buisson ◽  
P Kosec ◽  
C S Reynolds ◽  
D R Wilkins ◽  
...  
Keyword(s):  
Black Hole ◽  
Photon Counting ◽  
Black Hole Mass ◽  
X Ray ◽  
Excess Emission ◽  
Transient Source ◽  
Stable Circular Orbit ◽  
Soft State ◽  
Galactic Black Hole ◽  
Innermost Stable Circular Orbit

ABSTRACT The Galactic black hole X-ray binary MAXI J1820+070 had a bright outburst in 2018 when it became the second brightest X-ray source in the sky. It was too bright for X-ray CCD instruments such as XMM–Newton and Chandra, but was well observed by photon-counting instruments such as Neutron star Inner Composition Explorer (NICER) and Nuclear Spectroscopic Telescope Array(NuSTAR). We report here on the discovery of an excess-emission component during the soft state. It is best modelled with a blackbody spectrum in addition to the regular disc emission, modelled as either diskbb or kerrbb. Its temperature varies from about 0.9 to 1.1 keV, which is about 30–80 per cent higher than the inner disc temperature of diskbb. Its flux varies between 4 and 12 per cent of the disc flux. Simulations of magnetized accretion discs have predicted the possibility of excess emission associated with a non-zero torque at the innermost stable circular orbit (ISCO) about the black hole, which, from other NuSTAR studies, lies at about 5 gravitational radii or about 60 km (for a black hole, mass is $8\, {\rm M}_{\odot }$). In this case, the emitting region at the ISCO has a width varying between 1.3 and 4.6 km and would encompass the start of the plunge region where matter begins to fall freely into the black hole.

scholarly journals Possible ∼0.4 h X-ray quasi-periodicity from an ultrasoft active galactic nucleus

2020 ◽  
Vol 644 ◽  
pp. L9
Author(s):  
J. R. Song ◽  
X. W. Shu ◽  
L. M. Sun ◽  
Y. Q. Xue ◽  
C. Jin ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nucleus ◽  
Quiescent State ◽  
Black Hole Mass ◽  
Resonance Model ◽  
X Ray ◽  
Galactic Black Hole ◽  
Independent Observations ◽  
Extreme Variability ◽  
X Ray Binaries

RX J1301.9+2747 is an ultrasoft active galactic nucleus (AGN) with unusual X-ray variability that is characterized by a long quiescent state and a short-lived flare state. The X-ray flares are found to recur quasi-periodically on a timescale of 13−20 ks. Here, we report the analysis of the light curve in the quiescent state from two XMM-Newton observations spanning 18.5 years, along with the discovery of a possible quasi-periodic X-ray oscillation (QPO) with a period of ∼1500 s. The QPO is detected at the same frequency in the two independent observations, with a combined significance of > 99.89%. The QPO is in agreement with the relation between frequency and black hole mass (MBH) that has been reported in previous works for AGNs and Galactic black hole X-ray binaries (XRBs). The QPO frequency is stable over almost two decades, suggesting that it may correspond to the high-frequency type found in XRBs and originates, perhaps, from a certain disk resonance mode. In the 3:2 twin-frequency resonance model, our best estimate on the MBH range implies that a maximal black hole spin can be ruled out. We find that all ultrasoft AGNs reported so far display quasi-periodicities in the X-ray emission, suggesting a possible link on the part of the extreme variability phenomenon to the ultrasoft X-ray component. This indicates that ultrasoft AGNs could be the most promising candidates in future searches for X-ray periodicities.

scholarly journals NuSTAR and Swift Observations of the Extragalactic Black Hole X-ray Binaries

2021 ◽  
Author(s):  
Arghajit Jana ◽  
Sachindra Naik ◽  
Debjit Chatterjee ◽  
Gaurava K Jaisawal
Keyword(s):  
Black Hole ◽  
Thermal Emission ◽  
Light Curves ◽  
Telescope Array ◽  
X Ray ◽  
Soft State ◽  
Galactic Black Hole ◽  
Photon Index ◽  
X Ray Binaries ◽  
Emission Fraction

Abstract We present the results obtained from detailed spectral and timing studies of extra-galactic black hole X-ray binaries LMC X–1 and LMC X–3, using simultaneous observations with Nuclear Spectroscopic Telescope Array (NuSTAR) and Neil Gehrels Swift observatories. The combined spectra in the 0.5 − 30 keV energy range, obtained between 2014 and 2019, are investigated for both sources. We do not find any noticeable variability in 0.5 − 30 keV light curves, with 0.1 − 10 Hz fractional rms estimated to be <2 per cent. No evidence of quasi-periodic oscillations is found in the power density spectra. The sources are found to be in the high soft state during the observations with disc temperature Tin ∼ 1 keV, photon index, Γ > 2.5 and thermal emission fraction, fdisc > 80 per cent. An Fe Kα emission line is detected in the spectra of LMC X–1, though no such feature is observed in the spectra of LMC X–3. From the spectral modelling, the spins of the black holes in LMC X–1 and LMC X–3 are estimated to be in the range of 0.92 − 0.95 and 0.19 − 0.29, respectively. The accretion efficiency is found to be, η ∼ 0.13 and η ∼ 0.04 for LMC X–1 and LMC X–3, respectively.

scholarly journals Exploring the radial disc ionization profile of the black hole X-ray binary GRS 1915+105

2019 ◽  
Vol 492 (1) ◽  
pp. 405-412 ◽  
Author(s):  
Soumya Shreeram ◽  
Adam Ingram
Keyword(s):  
Black Hole ◽  
Relativistic Effects ◽  
X Rays ◽  
Ionization State ◽  
X Ray ◽  
Stable Circular Orbit ◽  
Inner Radius ◽  
Best Fitting ◽  
Innermost Stable Circular Orbit ◽  
Spectroscopy Studies

ABSTRACT Accreting black holes show characteristic ‘reflection’ features in their X-ray spectra, including the iron K α fluorescence line, which result from X-rays radiated by a compact central corona being reprocessed in the accretion disc atmosphere. The observed line profile is distorted by relativistic effects, providing a diagnostic for disc geometry. Nearly all previous X-ray reflection spectroscopy studies have made the simplifying assumption that the disc ionization state is independent of radius in order to calculate the rest-frame reflection spectrum. However, this is unlikely to be the case in reality, since the irradiating flux should drop off steeply with radius. Here, we analyse a Nuclear Spectroscopic Telescope Array observation of GRS 1915+105 that exhibits strong reflection features. We find that using a self-consistently calculated radial ionization profile returns a better fit than assuming constant ionization. Our results are consistent with the inner disc being radiation-pressure dominated, as is expected from the high inferred accretion rate for this observation. We also find that the assumed ionization profile impacts on the best-fitting disc inner radius. This implies that the black hole spin values previously inferred for active galactic nuclei and X-ray binaries by equating the disc inner radius with the innermost stable circular orbit may be changed significantly by the inclusion of a self-consistent ionization profile.

scholarly journals Estimation of the black hole spin in LMC X-1 using AstroSat

2020 ◽  
Vol 498 (3) ◽  
pp. 4404-4410
Author(s):  
Sneha Prakash Mudambi ◽  
A Rao ◽  
S B Gudennavar ◽  
R Misra ◽  
S G Bubbly
Keyword(s):  
Black Hole ◽  
Broad Band ◽  
Spectral Studies ◽  
Large Area ◽  
Mass Source ◽  
Orbital Inclination ◽  
X Ray ◽  
Soft State ◽  
Galactic Black Hole ◽  
Area X

ABSTRACT LMC X-1, a persistent, rapidly rotating, extra-galactic, black hole X-ray binary (BHXB) discovered in 1969, has always been observed in its high soft state. Unlike many other BHXBs, the black hole mass, source distance, and binary orbital inclination are well established. In this work, we report the results of simultaneous broad-band spectral studies of LMC X-1 carried out using the data from Soft X-ray Telescope and Large Area X-ray Proportional Counter aboard AstroSat as observed on 2016 November 26 and 2017 August 28. The combined spectrum was modelled with a multicolour blackbody emission (diskbb), a Gaussian along with a Comptonization component (simpl) in the energy range 0.7–30.0 keV. The spectral analysis revealed that the source was in its high soft state (Γ = 2.67$^{+0.24}_{-0.24}$ and Γ = 2.12$^{+0.19}_{-0.20}$) with a hot disc (kTin = 0.86$^{+0.01}_{-0.01}$ and kTin = 0.87$^{+0.02}_{-0.02}$). Thermal disc emission was fitted with a relativistic model (kerrbb) and spin of the black hole was estimated to be 0.93$^{+0.01}_{-0.01}$ and 0.93$^{+0.04}_{-0.03}$ (statistical errors) for the two Epochs through X-ray continuum-fitting, which agrees with the previous results.

scholarly journals Estimating the size of X-ray lamppost coronae in active galactic nuclei

2020 ◽  
Vol 644 ◽  
pp. A132
Author(s):  
F. Ursini ◽  
M. Dovčiak ◽  
W. Zhang ◽  
G. Matt ◽  
P.-O. Petrucci ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Stable Circular Orbit ◽  
Disc Area ◽  
Higher Spin ◽  
Photon Index ◽  
Innermost Stable Circular Orbit ◽  
Eddington Limit

Aims. We report estimates of the X-ray coronal size of active galactic nuclei in the lamppost geometry. In this commonly adopted scenario, the corona is assumed for simplicity to be a point-like X-ray source located on the axis of the accretion disc. However, the corona must intercept a number of optical/UV seed photons from the disc consistent with the observed X-ray flux, which constrains its size. Methods. We employ a relativistic ray-tracing code, originally developed by Dovčiak and Done, that calculates the size of a Comptonizing lamppost corona illuminated by a standard thin disc. We assume that the disc extends down to the innermost stable circular orbit of a non-spinning or a maximally spinning black hole. We apply this method to a sample of 20 Seyfert 1 galaxies using simultaneous optical/UV and X-ray archival data from XMM-Newton. Results. At least for the sources accreting below the Eddington limit, we find that a Comptonizing lamppost corona can generally exist, but with constraints on its size and height above the event horizon of the black hole depending on the spin. For a maximally spinning black hole, a solution can almost always be found at any height, while for a non-spinning black hole the height must generally be higher than 5 gravitational radii. This is because, for a given luminosity, a higher spin implies more seed photons illuminating the corona, which is due to a larger and hotter inner disc area. The maximal spin solution is favoured, as it predicts an X-ray photon index in better agreement with the observations.

scholarly journals The structure and emission of an inner disk and a corona in the low/hard state

2012 ◽  
Vol 8 (S290) ◽  
pp. 299-300
Author(s):  
Erlin Qiao ◽  
Bifang Liu
Keyword(s):  
Black Hole ◽  
X Ray ◽  
Stable Circular Orbit ◽  
Photon Index ◽  
Hard State ◽  
Innermost Stable Circular Orbit ◽  
Inner Region ◽  
Hot Corona ◽  
X Ray Binaries ◽  
Disk Component

AbstractRecent observations reveal that a cool disk may survive in the innermost stable circular orbit (ISCO) for some black hole X-ray binaries in the low/hard state. The spectrum is characterized by a power law with a photon index Γ ~ 1.5-2.1 in the range of 2-10 keV and a weak disk component with temperature of ~ 0.2 keV. The formation of such a cool disk in the most inner region of black hole X-ray binaries at the low/hard state is investigated within the framework of disk accretion fed by condensation of hot corona. We also calculate the emergent spectra of the inner disk and corona. It's found that our model can very well explain the spectral features of GX 339-4 and Cyg X-1, in which the thin disk may exist at ISCO in the low/hard state.

scholarly journals A maximum X-ray luminosity scale of disc-dominated tidal destruction events

2021 ◽  
Author(s):  
Andrew Mummery
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Compton Scattering ◽  
Large Mass ◽  
Accretion Disc ◽  
Black Hole Mass ◽  
X Ray ◽  
Soft State ◽  
Mass Outflow ◽  
Strong Agreement

Abstract We develop a model describing the dynamical and observed properties of disc-dominated TDEs around black holes with the lowest masses (M ≲ few × 106M⊙). TDEs around black holes with the lowest masses are most likely to reach super-Eddington luminosities at early times in their evolution. By assuming that the amount of stellar debris which can form into a compact accretion disc is set dynamically by the Eddington luminosity, we make a number of interesting and testable predictions about the observed properties of bright soft-state X-ray TDEs and optically bright, X-ray dim TDEs. We argue that TDEs around black holes of the lowest masses will expel the vast majority of their gravitationally bound debris into a radiatively driven outflow. A large-mass outflow will obscure the innermost X-ray producing regions, leading to a population of low black hole mass TDEs which are only observed at optical & UV energies. TDE discs evolving with bolometric luminosities comparable to their Eddington luminosity will have near constant (i.e. black hole mass independent) X-ray luminosities, of order LX, max ≡ LM ∼ 1043 − 1044 erg/s. The range of luminosity values stems primarily from the range of allowed black hole spins. A similar X-ray luminosity limit exists for X-ray TDEs in the hard (Compton scattering dominated) state, and we therefore predict that the X-ray luminosity of the brightest X-ray TDEs will be at the scale LM(a) ∼ 1043 − 1044 erg/s, independent of black hole mass and accretion state. These predictions are in strong agreement with the properties of the existing population (∼40 sources) of observed TDEs.

scholarly journals X-Ray Determination of the Black-Hole Mass in Cygnus X-1

1998 ◽  
Vol 188 ◽  
pp. 388-389
Author(s):  
A. Kubota ◽  
K. Makishima ◽  
T. Dotani ◽  
H. Inoue ◽  
K. Mitsuda ◽  
...  
Keyword(s):  
Black Hole ◽  
Compact Object ◽  
Optical Observations ◽  
Black Hole Mass ◽  
X Ray ◽  
Upper Limit ◽  
Supergiant Star ◽  
X Ray Binaries ◽  
Two Bodies

About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.

scholarly journals A full relativistic thin disc - the physics of the plunging region and the value of the stress at the ISCO

2021 ◽  
Author(s):  
William J Potter
Keyword(s):  
Black Hole ◽  
Surface Temperature ◽  
Accretion Rate ◽  
Speed Of Light ◽  
Thin Disc ◽  
Stable Circular Orbit ◽  
Stress Surface ◽  
Innermost Stable Circular Orbit ◽  
Turbulent Heating ◽  
Local Surface Temperature

Abstract The widely used Novikov-Thorne relativistic thin disc equations are only valid down to the radius of the innermost-stable circular orbit (ISCO). This leads to an undetermined boundary condition at the ISCO, known as the inner stress of the disc, which sets the luminosity of the disc at the ISCO and introduces considerable ambiguity in accurately determining the mass, spin and accretion rate of black holes from observed spectra. We resolve this ambiguity by self-consistently extending the relativistic disc solution through the ISCO to the black hole horizon by calculating the inspiral of an average disc particle subject to turbulent disc forces, using a new particle-in-disc technique. Traditionally it has been assumed that the stress at the ISCO is zero, with material plunging approximately radially into the black hole at close to the speed of light. We demonstrate that in fact the inspiral is less severe, with several (∼4 − 17) orbits completed before the horizon. This leads to a small non-zero stress and luminosity at and inside the ISCO, with a local surface temperature at the ISCO between ∼0.15 − 0.3 times the maximum surface temperature of the disc, in the case where no dynamically important net magnetic field is present. For a range of disc parameters we calculate the value of the inner stress/surface temperature, which is required when fitting relativistic thin disc models to observations. We resolve a problem in relativistic slim disc models in which turbulent heating becomes inaccurate and falls to zero inside the plunging region.

scholarly journals X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

2019 ◽  
Vol 15 (S356) ◽  
pp. 143-143
Author(s):  
Jaya Maithil ◽  
Michael S. Brotherton ◽  
Bin Luo ◽  
Ohad Shemmer ◽  
Sarah C. Gallagher ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Rate ◽  
Time Lags ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Massive Black Holes ◽  
X Ray ◽  
Photon Index ◽  
The Impact

AbstractActive Galactic Nuclei (AGN) exhibit multi-wavelength properties that are representative of the underlying physical processes taking place in the vicinity of the accreting supermassive black hole. The black hole mass and the accretion rate are fundamental for understanding the growth of black holes, their evolution, and the impact on the host galaxies. Recent results on reverberation-mapped AGNs show that the highest accretion rate objects have systematic shorter time-lags. These super-Eddington accreting massive black holes (SEAMBHs) show BLR size 3-8 times smaller than predicted by the Radius-Luminosity (R-L) relationship. Hence, the single-epoch virial black hole mass estimates of highly accreting AGNs have an overestimation of a factor of 3-8 times. SEAMBHs likely have a slim accretion disk rather than a thin disk that is diagnostic in X-ray. I will present the extreme X-ray properties of a sample of dozen of SEAMBHs. They indeed have a steep hard X-ray photon index, Γ, and demonstrate a steeper power-law slope, ασx.

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