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Echoes from an Irradiated Disc in GRO J1655-40

R. I. Hynes·K. O'Brien·Keith Horne·W. Chen·C. A. Haswell
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Abstract

We demonstrate correlated rapid variability between the optical/UV and X-ray emission for the first time in a soft X-ray transient, GRO J1655-40: HST light curves show similar features to those seen by RXTE, but with mean delay of 10-20s. We interpret the correlations as due to reprocessing of X-rays into optical and UV emission, with a delay due to finite light travel time, and thus perform echo mapping of the system. The time-delay distribution has a mean of 14.6s +/- 1.4 and dispersion (i.e. the standard deviation of the distribution) of 10.5s +/- 1.9 at binary phase 0.4. Hence we identify the reprocessing region as the accretion disc rather than the mass donor star.

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R. I. Hynes, K. O'Brien, Keith Horne, W. Chen, C. A. Haswell. 1998-06-02. Echoes from an Irradiated Disc in GRO J1655-40. https://doi.org/10.1046/j.1365-8711.1998.01856.x

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