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Published October 20, 2019 | Submitted + Published
Journal Article Open

Discovery and Identification of MAXI J1621-501 as a Type I X-ray Burster with a Super-Orbital Period

Abstract

MAXI J1621-501 is the first Swift/XRT Deep Galactic Plane Survey transient that was followed up with a multitude of space missions (NuSTAR, Swift, Chandra, NICER, INTEGRAL, and MAXI) and ground-based observatories (Gemini, IRSF, and ATCA). The source was discovered with MAXI on 2017 October 19 as a new, unidentified transient. Further observations with NuSTAR revealed 2 Type I X-ray bursts, identifying MAXI J1621-501 as a Low Mass X-ray Binary (LMXB) with a neutron star primary. Overall, 24 Type I bursts were detected from the source during a 15 month period. At energies below 10 keV, the source spectrum was best fit with three components: an absorbed blackbody with kT = 2.3 keV, a cutoff power law with index Γ = 0.7, and an emission line centered on 6.3 keV. Timing analysis of the X-ray persistent emission and burst data has not revealed coherent pulsations from the source or an orbital period. We identified, however, a super-orbital period ∼78 days in the source X-ray light curve. This period agrees very well with the theoretically predicted radiative precession period of ∼82 days. Thus, MAXI J1621-501 joins a small group of sources characterized with super-orbital periods.

Additional Information

© 2019 The American Astronomical Society. Received 2019 June 27; revised 2019 August 15; accepted 2019 August 21; published 2019 October 22. We thank the anonymous referee, whose comments improved the quality of this work. N.G., C.K., and P.B. acknowledge support from Chandra award number GO8-19061X and Swift award number NNH16ZDA001N-SWIFT. The IRSF project is supported by the Grants-in-Aid for Scientific Research on Priority Areas (A) (No. 10147207 and No. 10147214). H.N. acknowledges support from a Grant-in-Aid for Scientific Research (No. 16K05301). The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. Special thanks go to Nobuyuki Kawai, Christina Gilligan, and Jill Neeley for their indispensable roles in data acquisition for this project. D.H. acknowledges support from the DIRAC Institute in the Department of Astronomy at the University of Washington. The DIRAC Institute is supported through generous gifts from the Charles and Lisa Simonyi Fund for Arts and Sciences, and the Washington Research Foundation. 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. 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). We thank all operations, software and calibration teams contributing to the facilities used in this study for support with the execution and analysis of these observations. Facilities: Swift - Swift Gamma-Ray Burst Mission, Chandra - , NuSTAR - , NICER - , MAXI - , INTEGRAL - , ATCA - , IRSF - , Gemini - , ADS - , HEASARC. - Software: MIRIAD (Sault et al. 1995), Stingray (Huppenkothen et al. 2016, 2019), emcee (Foreman-Mackey et al. 2013), CIAO (v4.9.3; Fruscione et al. 2006), HEAsoft (v624; HEASARC 2014), XSPEC (v12.10.0; Arnaud 1996).

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Published - Gorgone_2019_ApJ_884_168.pdf

Submitted - 1908.03590.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 18, 2023