期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 334, 期 2, 页码 426-434出版社
BLACKWELL PUBLISHING LTD
DOI: 10.1046/j.1365-8711.2002.05530.x
关键词
accretion, accretion discs; binaries : close; stars : individual; Nova Sco 1994 (GRO J1655-40); ultraviolet : stars; X-rays : binaries; X-rays : stars
We present a method of analysing the correlated X-ray and optical/UV variability in X-ray binaries, using the observed time delays between the X-ray driving light curves and their reprocessed optical echoes. This allows us to determine the distribution of reprocessing sites within the binary. We model the time-delay transfer functions by simulating the distribution of reprocessing regions, using geometrical and binary parameters. We construct best-fitting time-delay transfer functions, showing the regions in the binary responsible for the reprocessing of X-rays. We have applied this model to observations of the soft X-ray transient GRO J1655-40. We find that the optical variability lags the X-ray variability with a mean time delay of 19.3+/-2.2 s. This means that the outer regions of the accretion disc are the dominant reprocessing site in this system. On fitting the data to a simple geometric model, we derive a best-fitting disc half-opening angle of 13.5(-2.8)(+2.1degrees), which is similar to that observed after the previous outburst by Orosz & Bailyn. This disc thickening has the effect of almost entirely shielding the companion star from irradiation at this stage of the outburst.
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