scholarly journals The X-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first Gyr of the Universe

2019 ◽  
Vol 630 ◽  
pp. A118 ◽  
Author(s):  
F. Vito ◽  
W. N. Brandt ◽  
F. E. Bauer ◽  
F. Calura ◽  
R. Gilli ◽  
...  
Keyword(s):  
Black Hole ◽  
Spectral Analysis ◽  
Statistical Tests ◽  
Average Power ◽  
X Ray ◽  
Photon Index ◽  
Accretion Physics ◽  
Bolometric Correction ◽  
Hot Corona ◽  
The Universe

Context. X-ray emission from quasars (QSOs) has been used to assess supermassive black hole accretion properties up to z ≈ 6. However, at z >  6 only ≈15 QSOs are covered by sensitive X-ray observations, preventing a statistically significant investigation of the X-ray properties of the QSO population in the first Gyr of the Universe. Aims. We present new Chandra observations of a sample of 10 z >  6 QSOs, selected to have virial black-hole mass estimates from Mg II line spectroscopy $ \left(\log\frac{M_{\mathrm{BH}}}{M_\odot}=8.5{-}9.6\right) $. Adding archival X-ray data for an additional 15 z >  6 QSOs, we investigate the X-ray properties of the QSO population in the first Gyr of the Universe. In particular, we focus on the LUV − LX relation, which is traced by the αox parameter, and the shape of their X-ray spectra. Methods. We performed photometric analyses to derive estimates of the X-ray luminosities of our z >  6 QSOs, and thus their αox values and bolometric corrections (Kbol = Lbol/LX). We compared the resulting αox and Kbol distributions with the results found for QSO samples at lower redshift, and ran several statistical tests to check for a possible evolution of the LUV − LX relation. Finally, we performed a basic X-ray spectral analysis of the brightest z >  6 QSOs to derive their individual photon indices, and joint spectral analysis of the whole sample to estimate the average photon index. Results. We detect seven of the new Chandra targets in at least one standard energy band, while two more are detected discarding energies E >  5 keV, where background dominates. We confirm a lack of significant evolution of αox with redshift, which extends the results from previous works up to z >  6 with a statistically significant QSO sample. Furthermore, we confirm the trend of an increasing bolometric correction with increasing luminosity found for QSOs at lower redshifts. The average power-law photon index of our sample (⟨Γ⟩ = 2.20−0.34+0.39 and ⟨Γ⟩ = 2.13−0.13+0.13 for sources with < 30 and > 30 net counts, respectively) is slightly steeper than, but still consistent with, typical QSOs at z = 1 − 6. Conclusions. All of these results indicate a lack of substantial evolution of the inner accretion-disk and hot-corona structure in QSOs from low redshift to z >  6. Our data hint at generally high Eddington ratios at z >  6.

scholarly journals Black hole masses from X-rays

2012 ◽  
Vol 8 (S290) ◽  
pp. 371-372
Author(s):  
Xin-Lin Zhou ◽  
Roberto Soria
Keyword(s):  
Black Hole ◽  
X Rays ◽  
X Ray ◽  
Reverberation Mapping ◽  
Photon Index ◽  
Bolometric Correction ◽  
Black Hole Masses ◽  
Intrinsic Scatter

AbstractWe discuss two methods to estimate black hole (BH) masses using X-ray data only: from the X-ray variability amplitude and from the photon index Γ. The first method is based on the anti-correlation between BH mass and X-ray variability amplitude. Using a sample of AGN with BH masses from reverberation mapping, we show that this method shows small intrinsic scatter. The second method is based on the correlation between Γ and both the Eddington ratio Lbol/LEdd and the bolometric correction Lbol/L2−10keV.

scholarly journals Evolution of the hard X-ray photon index in black-hole X-ray binaries: hints for accretion physics

2019 ◽  
Vol 487 (4) ◽  
pp. 5335-5345 ◽  
Author(s):  
Hao Liu ◽  
AiJun Dong ◽  
ShanShan Weng ◽  
Qingwen Wu
Keyword(s):  
Black Hole ◽  
Spectral Index ◽  
Decay Phase ◽  
X Ray ◽  
Initial Rise ◽  
Photon Index ◽  
Accretion Physics ◽  
Positive Correlations ◽  
X Ray Binaries ◽  
Rise Phase

ABSTRACT Negative and positive correlations between the X-ray photon index and the Eddington-scaled X-ray luminosity were found in the decay phase of X-ray binary outbursts and a sample of active galactic nuclei in former works. We systematically investigate the evolution of the X-ray spectral index, along with the X-ray flux and Eddington ratio, in eight outbursts of four black-hole X-ray binaries, where all selected outbursts have observational data from the Rossi X-ray Timing Explorer in both rise and decay phases. In the initial rise phase, the X-ray spectral index is anticorrelated with the flux and the X-ray spectrum quickly softens when the X-ray flux is approaching the peak value. In the decay phase, the X-ray photon index and the flux follow two different positive correlations and they become anticorrelated again when the X-ray flux is below a critical value, where the anticorrelation part follows the same trend as found in the initial rise phase. Compared with other X-ray binaries, GRO J1655−40 has an evident lower critical Eddington ratio for the anticorrelation and positive transition, which suggests that its black-hole mass and distance are not well constrained, or its intrinsic physics is different.

scholarly journals A NuSTAR census of coronal parameters in Seyfert galaxies

2018 ◽  
Vol 614 ◽  
pp. A37 ◽  
Author(s):  
A. Tortosa ◽  
S. Bianchi ◽  
A. Marinucci ◽  
G. Matt ◽  
P. O. Petrucci
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Optical Depth ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Black Hole Mass ◽  
Significance Level ◽  
X Ray ◽  
Photon Index ◽  
Hot Corona

Context. We discuss the results of the hot corona parameters of active galactic nuclei (AGN) that have been recently measured with NuSTAR. The values taken from the literature of a sample of 19 bright Seyfert galaxies are analysed. Aims. The aim of this work is to look for correlations between coronal parameters, such as the photon index and cut-off energy (when a phenomenological model is adopted) or the optical depth and temperature (when a Comptonization model is used), and other parameters of the systems, such as the black hole mass or the Eddington ratio. Methods. We analysed the coronal parameters of the 19 unobscured, bright Seyfert galaxies that are present in the Swift/BAT 70-month catalogue and that have been observed by NuSTAR, alone or simultaneously with others X-ray observatories, such as Swift, Suzaku, or XMM-Newton. Results. We found an anti-correlation with a significance level >98% between the coronal optical depth and the coronal temperature of our sample. On the other hand, no correlation between the above parameters and the black hole mass, the accretion rate, and the intrinsic spectral slope of the sources is found.

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 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.

scholarly journals Magnetar X-ray emission mechanisms

2012 ◽  
Vol 8 (S291) ◽  
pp. 160-160
Author(s):  
Silvia Zane
Keyword(s):  
Spectral Analysis ◽  
Physical Interpretation ◽  
Spectral Properties ◽  
Gamma Ray ◽  
X Ray ◽  
Spectral Components ◽  
Self Consistent ◽  
Photon Index ◽  
Index 2 ◽  
Surface Fields

AbstractSoft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are peculiar X-ray sources which are believed to be magnetars: ultra-magnetized neutron stars which emission is dominated by surface fields (often in excess of 1E14 G, i.e. well above the QED threshold).Spectral analysis is an important tool in magnetar astrophysics since it can provide key information on the emission mechanisms. The first attempts at modelling the persistent (i.e. outside bursts) soft X-ray (¡10 keV) spectra of AXPs proved that a model consisting of a blackbody (kT 0.3-0.6 keV) plus a power-law (photon index 2-4) could successfully reproduce the observed emission. Moreover, INTEGRAL observations have shown that, while in quiescence, magnetars emit substantial persistent radiation also at higher energies, up to a few hundreds of keV. However, a convincing physical interpretation of the various spectral components is still missing.In this talk I will focus on the interpretation of magnetar spectral properties during quiescence. I will summarise the present status of the art and the currents attempts to model the broadband persistent emission of magnetars (from IR to hard Xrays) within a self consistent, physical scenario.

scholarly journals Discovery of a New X-ray Transient in Scorpius GRO J1655-40 ≡ X-ray Nova Scorpii 1994

1996 ◽  
Vol 165 ◽  
pp. 363-367
Author(s):  
W.S. Paciesas ◽  
S.N. Zhang ◽  
B.C. Rubin ◽  
B.A. Harmon ◽  
C.A. Wilson ◽  
...  
Keyword(s):  
Black Hole ◽  
High Resolution ◽  
Power Law ◽  
Radio Observations ◽  
X Ray ◽  
Black Hole Candidate ◽  
Radio Jets ◽  
Transient Source ◽  
Galactic Source ◽  
Photon Index

A bright transient X-ray source, GRO J1655-40 (X-ray Nova Scorpii 1994) was discovered with BATSE (the Burst and Transient Source Experiment) in late July 1994. More recently, the source also became a strong radio emitter, its rise in the radio being approximately anti-correlated with a decline in the hard X-ray intensity. High-resolution radio observations subsequent to this symposium showed evidence for superluminally expanding jets. Since the hard X-ray emission extends to at least 200 keV and we find no evidence of pulsations, we tentatively classify the source as a black-hole candidate. However, its hard X-ray spectrum is unusually steep (power-law photon index α ≃ −3) relative to most other black-hole candidates. In this regard, it resembles GRS 1915+105, the first galactic source to show superluminal radio jets.

scholarly journals Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: observations and interpretation

2014 ◽  
Vol 447 (2) ◽  
pp. 1692-1704 ◽  
Author(s):  
Qi-Xiang Yang ◽  
Fu-Guo Xie ◽  
Feng Yuan ◽  
Andrzej A. Zdziarski ◽  
Marek Gierliński ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
Photon Index ◽  
X Ray Binaries

scholarly journals The photon-index–time-lag correlation in black hole X-ray binaries

2017 ◽  
Vol 473 (4) ◽  
pp. 4644-4652 ◽  
Author(s):  
Pablo Reig ◽  
Nikolaos D. Kylafis ◽  
Iossif E. Papadakis ◽  
María Teresa Costado
Keyword(s):  
Black Hole ◽  
Time Lag ◽  
X Ray ◽  
Photon Index ◽  
X Ray Binaries ◽  
Time Lag Correlation

scholarly journals A detailed study on the reflection component for the black hole candidate MAXI J1836−194

2020 ◽  
Vol 493 (2) ◽  
pp. 2178-2187
Author(s):  
Yanting Dong ◽  
Javier A García ◽  
Zhu Liu ◽  
Xueshan Zhao ◽  
Xueying Zheng ◽  
...  
Keyword(s):  
Black Hole ◽  
Spectral Analysis ◽  
Primary Source ◽  
Ionization State ◽  
X Ray ◽  
Black Hole Candidate ◽  
Reflection Model ◽  
Iron Abundance ◽  
Reflection Component ◽  
Ionization Gradient

ABSTRACT We present a detailed spectral analysis of the black hole candidate MAXI J1836−194. The source was caught in the intermediate state during its 2011 outburst by Suzaku and RXTE. We jointly fit the X-ray data from these two missions using the relxill model to study the reflection component, and a steep inner emissivity profile indicating a compact corona as the primary source is required in order to achieve a good fit. In addition, a reflection model with a lamp-post configuration (relxilllp), which is normally invoked to explain the steep emissivity profile, gives a worse fit and is excluded at 99 per cent confidence level compared to relxill. We also explore the effect of the ionization gradient on the emissivity profile by fitting the data with two relativistic reflection components, and it is found that the inner emissivity flattens. These results may indicate that the ionization state of the disc is not constant. All the models above require a supersolar iron abundance higher than ∼4.5. However, we find that the high-density version of reflionx can describe the same spectra even with solar iron abundance well. A moderate rotating black hole (a* = 0.84–0.94) is consistently obtained by our models, which is in agreement with previously reported values.

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