X-Ray Spectral Correlations in a Sample of Low-mass Black Hole X-Ray Binaries in the Hard State
Abstract The power-law emission and reflection component provide valuable insights into the accretion process around a black hole. In this work, thanks to the broadband spectra coverage of the Nuclear Spectroscopic Telescope Array, we study the spectral properties for a sample of low-mass black hole...
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Published in | The Astrophysical journal Vol. 945; no. 1; pp. 65 - 80 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
The American Astronomical Society
01.03.2023
IOP Publishing |
Subjects | |
Online Access | Get full text |
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Summary: | Abstract
The power-law emission and reflection component provide valuable insights into the accretion process around a black hole. In this work, thanks to the broadband spectra coverage of the Nuclear Spectroscopic Telescope Array, we study the spectral properties for a sample of low-mass black hole X-ray binaries (BHXRBs). We find that there is a positive correlation between the photon index Γ and the reflection fraction
R
(the ratio of the coronal intensity that illuminates the disk to the coronal intensity that reaches the observer), consistent with previous studies, but except for MAXI J1820+070. It is quite interesting that this source also deviates from the well-known “V”-shaped correlation between the photon index Γ and the X-ray luminosity
log
L
X
, when it is in the bright hard state. More specifically, the Λ-shaped correlation between Γ and log
L
X
is observed, as the luminosity decreases by a factor of 3 in a narrow range from ∼10
38
to 10
37.5
erg s
−1
. Furthermore, we discover a strong positive correlation between
R
and the X-ray luminosity for BHXRBs in the hard state, which puts a constraint on the disk-corona coupling and the evolution. |
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Bibliography: | AAS41109 High-Energy Phenomena and Fundamental Physics |
ISSN: | 0004-637X 1538-4357 |
DOI: | 10.3847/1538-4357/acba11 |