TY - JOUR
T1 - A 420-day X-ray/optical modulation and extended X-ray dips in the short-period transient Swift J1753.5-0127
AU - Shaw, A. W.
AU - Charles, P. A.
AU - Bird, A. J.
AU - Cornelisse, R.
AU - Casares, J.
AU - Lewis, F.
AU - Muñoz-Darias, T.
AU - Russell, D. M.
AU - Zurita, C.
PY - 2013/7
Y1 - 2013/7
N2 - 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.
AB - 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.
KW - X-rays:individual:swift J1753.5-0127
UR - http://www.scopus.com/inward/record.url?scp=84880440653&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84880440653&partnerID=8YFLogxK
U2 - 10.1093/mnras/stt763
DO - 10.1093/mnras/stt763
M3 - Article
AN - SCOPUS:84880440653
SN - 0035-8711
VL - 433
SP - 740
EP - 745
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -