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

Xu, Yanjun and Harrison, Fiona A. and García, Javier A. and Fabian, Andrew C. and Fürst, Felix and Gandhi, Poshak and Grefenstette, Brian W. and Madsen, Kristin K. and Miller, Jon M. and Parker, Michael L. and Tomsick, John A. and Walton, Dominic J. (2018) Reflection Spectra of the Black Hole Binary Candidate MAXI J1535-571 in the Hard State Observed by NuSTAR. Astrophysical Journal Letters, 852 (2). Art. No. L34. ISSN 2041-8213. doi:10.3847/2041-8213/aaa4b2.

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We report on a Nuclear Spectroscopic Telescope Array (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 Kα line and a Compton hump peaking around 30 keV. Detailed spectral modeling reveals a narrow Fe Kα line complex centered around 6.5 keV on top of the strong relativistically broadened Fe Kα 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 kT_e = 19.7 ± 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_(in) < 2.01 r_(ISCO) , and a lamp-post height h = 7.2^(+0.8)_(-2.0) r_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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Xu, Yanjun0000-0003-2443-3698
Harrison, Fiona A.0000-0003-2992-8024
García, Javier A.0000-0003-3828-2448
Fabian, Andrew C.0000-0002-9378-4072
Fürst, Felix0000-0003-0388-0560
Gandhi, Poshak0000-0003-3105-2615
Grefenstette, Brian W.0000-0002-1984-2932
Madsen, Kristin K.0000-0003-1252-4891
Parker, Michael L.0000-0002-8466-7317
Tomsick, John A.0000-0001-5506-9855
Walton, Dominic J.0000-0001-5819-3552
Additional Information:© 2018 The American Astronomical Society. Received 2017 November 2; revised 2018 January 2; accepted 2018 January 2; published 2018 January 12. We thank the referee for constructive comments that improved the Letter. D.J.W. acknowledges support from STFC Ernest Rutherford Fellowship. J.A.G. acknowledges support from NASA grant No. 80NSSC17K0515 and the Alexander von Humboldt Foundation. This work was supported under NASA contract No. NNG08FD60C and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software, and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS), jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA).
Group:NuSTAR, Space Radiation Laboratory, Astronomy Department
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Subject Keywords:accretion, accretion disks – black hole physics – X-rays: binaries
Issue or Number:2
Record Number:CaltechAUTHORS:20180116-152713791
Persistent URL:
Official Citation:Yanjun Xu et al 2018 ApJL 852 L34
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84345
Deposited By: Tony Diaz
Deposited On:17 Jan 2018 18:59
Last Modified:15 Nov 2021 20:19

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