Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR

Abstract

We report on a NuSTAR observation of the recently discovered bright black hole candidate MAXI J1535-571. NuSTAR observed the source on MJD 58003 (five days after the outburst was reported). The spectrum is characteristic of a black hole binary in the hard state. We observe clear disk reflection features, including a broad Fe K$\alpha$ line and a Compton hump peaking around 30 keV. Detailed spectral modeling reveals narrow Fe K$\alpha$ line complex centered around 6.5 keV on top of the strong relativistically broadened Fe K$\alpha$ line. The narrow component is consistent with distant reflection from moderately ionized material. The spectral continuum is well described by a combination of cool thermal disk photons and a Comptonized plasma with the electron temperature $k{T}_{\mathrm{e}}=19.7\pm 0.4$ keV. An adequate fit can be achieved for the disk reflection features with a self-consistent relativistic reflection model that assumes a lamp-post geometry for the coronal illuminating source. The spectral fitting measures a black hole spin $a>0.84$, inner disk radius $R_{\mathrm{in}}<2.01r_{\mathrm{ISCO}}$, and a lamp-post height $h=7.2_{-2.0}^{+0.8}{r}_{\mathrm{g}}$ (statistical errors, 90% confidence), indicating no significant disk truncation and a compact corona. Although the distance and mass of this source are not currently known, this suggests the source was likely in the brighter phases of the hard state during this NuSTAR observation.

accepted for publication in ApJL

References in corpus (6)

• X-ray Properties of Black-Hole Binaries
• The role of the reflection fraction in constraining black hole spin
• A quasi-periodic modulation of the iron line centroid energy in the black hole binary H 1743-322
• Broadband X-ray Imaging and Spectroscopy of the Crab Nebula and Pulsar with NuSTAR
• New Constraints on the Black Hole Low/Hard State Inner Accretion Flow with NuSTAR
• Hard X-ray emission of the microquasar GRO J1655-40 during the rise of its 2005 outburst

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• Broadband reflection spectroscopy of MAXI J1535-571 using AstroSat: Estimation of black hole mass and spin
• A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR
• NuSTAR observations of the Transient Galactic Black Hole Binary Candidate Swift J1858.6-0814: A New Sibling of V404 Cyg and V4641 Sgr?
• Broadband X-ray Spectral and Timing Analyses of the Black Hole Binary Candidate Swift J1658.2-4242: Rapid Flux Variation and the Turn-on of a Transient QPO
• A detailed study on the reflection component for the Black Hole Candidate MAXI J1836-194
• Broadband X-ray analysis of 1E 1740.7-2942: constraints on spin, inclination and a tentative black hole mass