Title:	X-ray and optical orbital modulation of EXO 0748-676: A co-variability study using XMM-Newton
Authors:	Raman, Gayathri Paul, Biswajit
Keywords:	Binaries: eclipsing Neutron stars
Issue Date:	Jul-2017
Publisher:	Elsevier B. V.
Citation:	New Astronomy, 2017, Vol. 54, p122-139
Abstract:	We present a multi-wavelength timing study of the eclipsing low mass X-ray binary EXO 0748-676 (UY Vol) using XMM-Newton when the source was in a hard spectral state. The orbital optical and X-ray light curves show a fairly large amount of intensity modulation in the 7 observations taken during September-November, 2003, covering 36 complete binary orbits of EXO 0748-676. While assessing the non-burst variability, simultaneously in the optical and X-ray light curves, we find that they are not correlated at reprocessing or orbital time-scales, but are weakly correlated at a few 1000s of seconds time-scales. Although a large fraction of the optical emission is likely to be due to reprocessing, the lack of significant correlation and presence of large variability in the orbital X-ray and optical light curves is probably due to structures and structural changes in the accretion disk that produce, and sometimes mask the reprocessed signal in varying amounts. These disk structures could be induced, at least partly, by irradiation. From the observed modulations seen in the optical light curves, there is strong evidence of accretion disk evolution at time scales of a few hours.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/6685
ISSN:	1384-1076
Alternative Location:	http://arxiv.org/abs/1702.03719 http://dx.doi.org/10.1016/j.newast.2017.02.001
Copyright:	2017 Elesvier B.V.
Appears in Collections:	Research Papers (A&A)

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