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arXiv · 1507.00149

K2 and MAXI observations of Sco X-1 - Evidence for disc precession?

Pasi Hakala·Gavin Ramsay·Thomas Barclay·Phil Charles
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Abstract

Sco X-1 is the archetypal low mass X-ray binary (LMXB) and the brightest persistent extra-solar X-ray source in the sky. It was included in the K2 Campaign 2 field and was observed continuously for 71 days with 1 minute time resolution. In this paper 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 timescales less than 3 hours (or 0.15 orbits). We also find evidence that this behaviour has a typical systemic timescale of 4.8 days, which we interpret as a possible disc precession period in the system. Finally, we confirm the complex optical vs. X-ray correlation/anticorrelation behaviour for "high" and "low" optical states respectively.

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Pasi Hakala, Gavin Ramsay, Thomas Barclay, Phil Charles. 2015-07-01. K2 and MAXI observations of Sco X-1 - Evidence for disc precession?. https://arxiv.org/abs/1507.00149

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