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تسجيل مستخدم جديدA NICER Spectrum of MAXI J1535-571: Near-Maximal Black Hole Spin and Potential Disk Warping
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J. M. Miller
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We report on a NICER observation of the Galactic X-ray binary and stellar-mass black hole candidate, MAXI J1535-571. The source was likely observed in an intermediate or very high state, with important contributions from both an accretion disk and hard X-ray corona. The 2.3-10 keV spectrum shows clear hallmarks of relativistic disk reflection. Fits with a suitable model strongly indicate a near-maximal spin parameter of a = cJ/GM^2 = 0.994(2) and a disk that extends close to the innermost stable circular orbit, r/r_ISCO = 1.08(8) (1-sigma statistical errors). In addition to the relativistic spectrum from the innermost disk, a relatively narrow Fe K emission line is also required. The resolution of NICER reveals that the narrow line may be asymmetric, indicating a specific range of emission radii. Fits with a relativistic line model suggest an inner radius of r = 144 (+140,-60) GM/c^2 for the putative second reflection geometry; full reflection models suggest that radii a few times larger are possible. The origin of the narrow line is uncertain but a warp likely provides the most physically plausible explanation. We discuss our results in terms of the potential for NICER to reveal new features of the inner and intermediate accretion disk around black holes.
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The black hole candidate and X-ray binary MAXI J1535-571 was discovered in September 2017. During the decay of its discovery outburst, and before returning to quiescence, the source underwent at least four reflaring events, with peak luminosities of
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We report the results from textit{AstroSat} observations of the transient Galactic black hole X-ray binary MAXI J1535-571 during its hard-intermediate state of the 2017 outburst. We systematically study the individual and joint spectra from two simul
taneously observing textit{AstroSat} X-ray instruments, and probe and measure a number of parameter values of accretion disc, corona and reflection from the disc in the system using models with generally increasing complexities. Using our broadband ($1.3-70$ keV) X-ray spectrum, we clearly show that a soft X-ray instrument, which works below $sim 10-12$ keV, alone cannot correctly characterize the Comptonizing component from the corona, thus highlighting the importance of broadband spectral analysis. By fitting the reflection spectrum with the latest version of the textsc{relxill} family of relativistic reflection models, we constrain the black holes dimensionless spin parameter to be $0.67^{+0.16}_{-0.04}$. We also jointly use the reflection spectral component (textsc{relxill}) and a general relativistic thin disc component (texttt{Kerrbb}), and estimate the black holes mass and distance to be $10.39_{-0.62}^{+0.61} M_{odot}$ and $5.4_{-1.1}^{+1.8}$ kpc respectively.
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