Correlated optical and X-ray variability in LMC X-2 |
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| Authors: | K E McGowan P A Charles D O'Donoghue A P Smale |
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| Institution: | Los Alamos National Laboratory, MS D436, Los Alamos, NM 87545, USA;Department of Physics, University of Oxford, Oxford OX1 3RH;Department of Physics and Astronomy, University of Southampton, Southampton S017 1BJ;South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa;Laboratory for High Energy Astrophysics, Code 662, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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| Abstract: | We have obtained high time resolution (seconds) photometry of LMC X-2 in 1997 December, simultaneously with the Rossi X-ray Timing Explorer ( RXTE ), in order to search for correlated X-ray and optical variability on time-scales from seconds to hours. We find that the optical and X-ray data are correlated only when the source is in a high, active X-ray state. Our analysis shows evidence for the X-ray emission leading the optical with a mean delay of <20 s. The time-scale for the lag can be reconciled with disc reprocessing, driven by the higher-energy X-rays, only by considering the lower limit for the delay. The results are compared with a similar analysis of archival data of Sco X-1. |
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| Keywords: | binaries: close stars: individual: LMC X-2 stars: individual: Sco X-1 X-rays: stars |
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