SXP 15.6 - an accreting pulsar close to spin equilibrium?

M. J. Coe, I. M. Monageng, J. A. Kennea, D. A.H. Buckley, P. A. Evans, A. Udalski, Paul Groot, Steven Bloemen, Paul Vreeswijk, Vanessa McBride, Marc Klein-Wolt, Patrick Woudt, Elmar Körding, Rudolf Le Poole, Danielle Pieterse

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SXP 15.6 is a recently established Be star X-ray binary system in the Small Magellanic Cloud (SMC). Like many such systems, the variable X-ray emission is driven by the underlying behaviour of the mass donor Be star. It is shown here that the neutron star in this system is exceptionally close to spin equilibrium averaged over several years, with the angular momentum gain from mass transfer being almost exactly balanced by radiative losses. This makes SXP 15.6 exceptional compared to all other known members of its class in the SMC, all of whom exhibit much higher spin period changes. In this paper, we report on X-ray observations of the brightest known outburst from this system. These observations are supported by contemporaneous optical and radio observations, as well as several years of historical data.

Original languageEnglish (US)
Pages (from-to)5567-5574
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jul 1 2022

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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