X-ray spectral and timing studies of black hole transients in the hard state at low luminosity

ABSTRACT X-ray signatures of outflowing gas have been detected in several accreting black hole binaries, always in the soft state. A key question raised by these observations is whether these winds might also exist in the hard state. Here, we carry out the first full-frequency radiation hydrodynamic simulations of luminous (${L = 0.5 \, L_{\mathrm{\mathrm{ Edd}}}}$) black hole X-ray binary systems in both the hard and the soft state, with realistic spectral energy distributions (SEDs). Our simulations are designed to describe X-ray transients near the peak of their outburst, just before and after the hard-to-soft state transition. At these luminosities, it is essential to include radiation driving, and we include not only electron scattering, but also photoelectric and line interactions. We find powerful outflows with ${\dot{M}_{\mathrm{ wind}} \simeq 2 \, \dot{M}_{\mathrm{ acc}}}$ are driven by thermal and radiation pressure in both hard and soft states. The hard-state wind is significantly faster and carries approximately 20 times as much kinetic energy as the soft-state wind. However, in the hard state the wind is more ionized, and so weaker X-ray absorption lines are seen over a narrower range of viewing angles. Nevertheless, for inclinations ≳80°, blueshifted wind-formed Fe xxv and Fe xxvi features should be observable even in the hard state. Given that the data required to detect these lines currently exist for only a single system in a luminous hard state – the peculiar GRS 1915+105 – we urge the acquisition of new observations to test this prediction. The new generation of X-ray spectrometers should be able to resolve the velocity structure.

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A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2711 ◽

2020 ◽

Vol 498 (4) ◽

pp. 5873-5884

Author(s):

Sudip Chakraborty ◽

Nilam Navale ◽

Ajay Ratheesh ◽

Sudip Bhattacharyya

Keyword(s):

Black Hole ◽

Broad Band ◽

X Ray ◽

Reflection Model ◽

Temporal Features ◽

Source State ◽

Hard State ◽

Independent Observations ◽

Best Fitting ◽

Fitting Model

ABSTRACT MAXI J1820+070 is a newly discovered transient black hole X-ray binary, which showed several spectral and temporal features. In this work, we analyse the broad-band X-ray spectra from all three simultaneously observing X-ray instruments onboard AstroSat, as well as contemporaneous X-ray spectra from NuSTAR, observed during the hard state of MAXI J1820+070 in 2018 March. Implementing a combination of multicolour disc model, relativistic blurred reflection model relxilllpcp, and a distant reflection in the form of xillvercp, we achieve reasonable and consistent fits for AstroSat and NuSTAR spectra. The best-fitting model suggests a low temperature disc (kTin ∼ 0.3 keV), iron overabundance (AFe ∼ 4–5 solar), a short lamp-post corona height (h ≲ 8Rg), and a high corona temperature (kTe ∼ 115–150 keV). Addition of a second Comptonization component leads to a significantly better fit, with the kTe of the second Comptonization component being ∼14–18 keV. Our results from independent observations with two different satellites in a similar source state indicate an inhomogeneous corona, with decreasing temperature attributed to increasing height. Besides, utilizing the broader energy coverage of AstroSat, we estimate the black hole mass to be 6.7–13.9 M⊙, consistent with independent measurements reported in the literature.

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

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa120 ◽

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.

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Hard state neutron star and black hole X-ray binaries in the radio:X-ray luminosity plane

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/sly083 ◽

2018 ◽

Vol 478 (1) ◽

pp. L132-L136 ◽

Cited By ~ 33

Author(s):

Elena Gallo ◽

Nathalie Degenaar ◽

Jakob van den Eijnden

Keyword(s):

Black Hole ◽

Neutron Star ◽

X Ray ◽

Hard State ◽

X Ray Binaries

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On the Properties of Inner Cool Disks in the Hard State of Black Hole X‐Ray Transient Systems

The Astrophysical Journal ◽

10.1086/591901 ◽

2008 ◽

Vol 688 (1) ◽

pp. 527-536 ◽

Cited By ~ 36

Author(s):

Ronald E. Taam ◽

B. F. Liu ◽

F. Meyer ◽

E. Meyer‐Hofmeister

Keyword(s):

Black Hole ◽

X Ray ◽

Hard State

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ON THE NATURE OF THE X-RAY CORONA OF BLACK HOLE BINARIES

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194512004448 ◽

2012 ◽

Vol 08 ◽

pp. 73-83 ◽

Cited By ~ 6

Author(s):

JULIEN MALZAC

Keyword(s):

Black Hole ◽

High Energy ◽

State Transitions ◽

Physical Parameters ◽

X Ray ◽

Black Hole Binaries ◽

Accretion Flow ◽

Recent Developments ◽

Hard State ◽

Radiation Processes

We discuss the nature of the X-ray emitting plasma of black hole binaries. It is well known that the temperature and optical depth of the Comptonising electrons of the X-ray corona of black hole binaries can be measured using spectroscopy in the 1 keV-1 MeV energy band. We emphasize recent developments in the modeling of high energy radiation processes which allow us to constrain other important physical parameters of the corona, such as the strength of magnetic field, or the temperature of the ions. The results appear to challenge current accretion models. In particular, standard advection dominated accretion flow do not match the observed properties of bright hard state X-ray binaries such as Cygnus X-1 or GX 339-4. On the other hand, we find that all the data would be consistent with a multi-zone magnetically dominated hot accretion flow model. We also emphasize that besides the usual spectral state transitions observed at luminosities above a few percent of Eddington, there is observational evidence for at least two additional, more subtle, radiative transitions occuring at lower luminosities.

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Wind accretion in Cygnus X-1

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037561 ◽

2020 ◽

Vol 637 ◽

pp. A66 ◽

Cited By ~ 1

Author(s):

E. Meyer-Hofmeister ◽

B. F. Liu ◽

E. Qiao ◽

R. E. Taam

Keyword(s):

Black Hole ◽

Stellar Wind ◽

Binary Systems ◽

Three Dimensional ◽

Stable States ◽

X Ray ◽

Hard State ◽

Hard Spectrum ◽

Low Mass ◽

Hydrodynamical Simulations

Context. Cygnus X-1 is a black hole X-ray binary system in which the black hole captures and accretes gas from the strong stellar wind emitted by its supergiant O9.7 companion star. The irradiation of the supergiant star essentially determines the flow properties of the stellar wind and the X-ray luminosity from the system. The results of three-dimensional hydrodynamical simulations of wind-fed X-ray binary systems reported in recent work reveal that the ionizing feedback of the X-ray irradiation leads to the existence of two stable states with either a soft or a hard spectrum. Aims. We discuss the observed radiation of Cygnus X-1 in the soft and hard state in the context of mass flow in the corona and disk, as predicted by the recent application of a condensation model. Methods. The rates of gas condensation from the corona to the disk for Cygnus X-1 are determined, and the spectra of the hard and soft radiation are computed. The theoretical results are compared with the MAXI observations of Cygnus X-1 from 2009 to 2018. In particular, we evaluate the hardness-intensity diagrams (HIDs) for its ten episodes of soft and hard states which show that Cygnus X-1 is distinct in its spectral changes as compared to those found in the HIDs of low-mass X-ray binaries. Results. The theoretically derived values of photon counts and hardness are in approximate agreement with the observed data in the HID. However, the scatter in the diagram is not reproduced. Improved agreement could result from variations in the viscosity associated with clumping in the stellar wind and corresponding changes of the magnetic fields in the disk. The observed dipping events in the hard state may also contribute to the scatter and to a harder spectrum than predicted by the model.

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