A1 Journal article – refereed
K2 and MAXI observations of Sco X-1 evidence for disc precession?




List of Authors: Hakala P, Ramsay G, Barclay T, Charles P
Publisher: OXFORD UNIV PRESS
Publication year: 2015
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume number: 453
ISSN: 0035-8711

Abstract


Sco X-1 is the archetypal low-mass X-ray binary and the brightest persistent extrasolar X-ray source in the sky. It was included in the K2 Campaign 2 field and was observed continuously for 71 d with 1 min time resolution. In this Letter, we report these results and underline the potential of K2 for similar observations of other accreting compact binaries. We reconfirm that Sco X-1 shows a bimodal distribution of optical 'high' and 'low' states and rapid transitions between them on time-scales less than 3 h (or 0.15 orbits). We also find evidence that this behaviour has a typical systemic time-scale of 4.8 d, which we interpret as a possible disc precession period in the system. Finally, we confirm the complex optical versus X-ray correlation/anticorrelation behaviour for 'high' and 'low' optical states, respectively.



Last updated on 2019-20-07 at 07:59