A 420-day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127

A. W. Shaw, P. A. Charles, A. J. Bird, R. Cornelisse, J. Casares, F. Lewis, T. Muñoz-Darias, D. M. Russell, C. Zurita

Research output: Contribution to journalArticlepeer-review

Abstract

We have discovered a ~420-d modulation, with associated X-ray dips, in Rossi X-Ray Timing Explorer-All Sky Monitor/Monitor of All-Sky X-ray Image/Swift-Burst Alert Telescope archival light curves of the short-period (3.2 h) black holeX-ray transient, Swift J1753.5-0127. This modulation only appeared at the end of a gradual re-brightening, approximately 3 yr after the initial X-ray outburst in mid-2005. The same periodicity is present in both the 2-20 and 15-50 keV bands, but with a ~0.1 phase offset (≈40 d). Contemporaneous photometry in the optical and near-infrared reveals a weaker modulation, but consistent with the X-ray period. There are two substantial X-ray dips (very strong in the 15-50 keV band, weaker at lower energies) that are separated by an interval equal to the X-ray period. This likely indicates two physically separated emitting regions for the hard X-ray and lower energy emission. We interpret this periodicity as a property of the accretion disc, most likely a long-term precession, where the disc edge structure and X-ray irradiation are responsible for the hard X-ray dips and modulation, although we discuss other possible explanations, including Lense-Thirring precession in the inner disc region and spectral state variations. Such precession indicates a very high mass ratio low-mass X-ray binary, which even for a ~10M· BH requires a brown dwarf donor (~0.02MM·), making Swift J1753.5-0127 a possible analogue of millisecond X-ray pulsars. We compare the properties of Swift J1753.5-0127 with other recently discovered short-period transients, which are now forming a separate population of high-latitude BH transients located in the galactic halo.

Original languageEnglish (US)
Pages (from-to)740-745
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society
Volume433
Issue number1
DOIs
StatePublished - Jul 2013

Keywords

  • X-rays:individual:swift J1753.5-0127

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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