A rare outburst from the stealthy BeXRB system Swift J0549.7-6812

M. J. Coe, J. A. Kennea, I. M. Monageng, D. A.H. Buckley, A. Udalski, P. A. Evans

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Swift J0549.7 -6812 is a Be/X-ray binary system (BeXRB) in the Large Magellanic Cloud (LMC) exhibiting an ~6 s pulse period. Like many such systems, the variable X-ray emission is believed to be driven by the underlying behaviour of the mass donor Be star. In this paper, we report on X-ray observations of the brightest known outburst from this system, which reached a luminosity of ~8 × 1037 erg s-1. These observations are supported by contemporaneous optical photometric observations, the first reported optical spectrum, as well as several years of historical data from Optical Gravitational Lens Explorer (OGLE) and Gaia . The latter strongly suggest a binary period of 46.1 d. All the observational data indicate that Swift J0549.7 -6812 is a system that spends the vast majority of its time in X-ray quiescence, or even switched off completely. This suggests that occasional observations may easily miss it, and many similar systems, and thereby underestimate the massive star evolution numbers for the LMC.

Original languageEnglish (US)
Pages (from-to)3263-3269
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Sep 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this