Discovery and Identification of MAXI J1621-501 as a Type i X-Ray Burster with a Super-orbital Period

Nicholas M. Gorgone, Chryssa Kouveliotou, Hitoshi Negoro, Ralph A.M.J. Wijers, Enrico Bozzo, Sylvain Guiriec, Peter Bult, Daniela Huppenkothen, Ersin Göǧüş, Arash Bahramian, Jamie Kennea, Justin D. Linford, James Miller-Jones, Matthew G. Baring, Paz Beniamini, Deepto Chakrabarty, Jonathan Granot, Charles Hailey, Fiona A. Harrison, Dieter H. HartmannWataru Iwakiri, Lex Kaper, Erin Kara, Simona Mazzola, Katsuhiro Murata, Daniel Stern, John A. Tomsick, Alexander J.Van Der Horst, George A. Younes

Research output: Contribution to journalArticlepeer-review


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 two Type I X-ray bursts, identifying MAXI J1621-501 as a low mass x-ray binary 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.

Original languageEnglish
Article number168
JournalAstrophysical Journal
Issue number2
StatePublished - 20 Oct 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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