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Spectral and Timing Analysis of NuSTAR and Swift/XRT Observations of the X-Ray Transient MAXI J0637–430

Lazar, Hadar and Tomsick, John A. and Pike, Sean N. and Bachetti, Matteo and Buisson, Douglas J. K. and Connors, Riley M. T. and Fabian, Andrew C. and Fuerst, Felix and García, Javier A. and Hare, Jeremy and Jiang, Jiachen and Shaw, Aarran W. and Walton, Dominic J. (2021) Spectral and Timing Analysis of NuSTAR and Swift/XRT Observations of the X-Ray Transient MAXI J0637–430. Astrophysical Journal, 921 (2). Art. No. 155. ISSN 0004-637X. doi:10.3847/1538-4357/ac1bab.

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We present results for the first observed outburst from the transient X-ray binary source MAXI J0637–430. This study is based on eight observations from the Nuclear Spectroscopic Telescope Array (NuSTAR) and six observations from the Neil Gehrels Swift Observatory X-Ray Telescope (Swift/XRT) collected from 2019 November 19 to 2020 April 26 as the 3–79 keV source flux declined from 8.2 × 10⁻¹⁰ to 1.4 × 10⁻¹² erg cm⁻² s⁻¹. We see the source transition from a soft state with a strong disk-blackbody component to a hard state dominated by a power-law or thermal Comptonization component. NuSTAR provides the first reported coverage of MAXI J0637–430 above 10 keV, and these broadband spectra show that a two-component model does not provide an adequate description of the soft-state spectrum. As such, we test whether blackbody emission from the plunging region could explain the excess emission. As an alternative, we test a reflection model that includes a physical Comptonization continuum. Finally, we also test a spectral component based on reflection of a blackbody illumination spectrum, which can be interpreted as a simple approximation to the reflection produced by returning disk radiation due to the bending of light by the strong gravity of the black hole. We discuss the physical implications of each scenario and demonstrate the value of constraining the source distance.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lazar, Hadar0000-0002-2752-9524
Tomsick, John A.0000-0001-5506-9855
Pike, Sean N.0000-0002-8403-0041
Bachetti, Matteo0000-0002-4576-9337
Connors, Riley M. T.0000-0002-8908-759X
Fabian, Andrew C.0000-0002-9378-4072
Fuerst, Felix0000-0003-0388-0560
García, Javier A.0000-0003-3828-2448
Hare, Jeremy0000-0002-8548-482X
Jiang, Jiachen0000-0002-9639-4352
Shaw, Aarran W.0000-0002-8808-520X
Walton, Dominic J.0000-0001-5819-3552
Additional Information:© 2021. The American Astronomical Society. Received 2021 June 17; revised 2021 July 28; accepted 2021 August 5; published 2021 November 10. This work 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). This work also made use of data from the Neil Gehrels Swift Observatory. H.L. and J.A.T. acknowledge partial support under NASA NuSTAR Guest Investigator grant 80NSSC20K0644. J.H. acknowledges support from an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by the Universities Space Research Association under contract with NASA. J.A.G. acknowledges support from NASA NuSTAR Guest Investigator grant 80NSSC20K1238, and from the Alexander von Humboldt Foundation. J.J. acknowledges support from the fellowship of China Postdoctoral Science Foundation (2021M691822), the Tsinghua Shuimu Scholar Program and the Tsinghua Astrophysics Outstanding Fellowship. Thank you to Dr. Thomas Dauser and Dr. Jack Steiner for the useful comments along the way. Facilities: NuSTAR - The NuSTAR (Nuclear Spectroscopic Telescope Array) mission, Swift/XRT - . Software: XSPEC (v12.11.1c Arnaud 1996), HEAsoft (v6.27.2), relxill suite (Dauser et al. 2014; García et al. 2014).
Group:Space Radiation Laboratory, NuSTAR
Funding AgencyGrant Number
NASA Postdoctoral ProgramUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
China Postdoctoral Science Foundation2021M691822
Tsinghua UniversityUNSPECIFIED
Subject Keywords:Accretion; Low-mass x-ray binary stars; Black hole physics
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Accretion (14); Low-mass x-ray binary stars (939); Black hole physics (159)
Record Number:CaltechAUTHORS:20211123-234017978
Persistent URL:
Official Citation:Hadar Lazar et al 2021 ApJ 921 155
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112026
Deposited By: Tony Diaz
Deposited On:24 Nov 2021 19:16
Last Modified:24 Nov 2021 19:16

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