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K.L. Brock (Bates Coll. and Maria Mitchell Obs.), G.C. Clayton (Louisiana State U. and Maria Mitchell Obs.), E.R. Wollman (Bates Coll.)
Eye estimates of the photographic magnitudes of the X-ray binary A0538-66 were done to an accuracy of ±0.5 magnitude on 91 plates from the Harvard College Observatory collection covering the period from 1897 to 1951. The archival data confirms the presence of the 16.651-day periodicity first discovered in X-ray observations and subsequently seen in the visible. Ten outbursts of about a magnitude or more were found in the archival data, all occurring within 3.3 days of ephemeris maxima of the 16.651-day cycle. However, the majority of the plates close to ephemeris maxima do not show significant brightening of the star, indicating that the on-off behavior seen in recent years also operated during the years of the archival data. We are investigating a possible correlation of the outbursts with the 420.8-day visible periodicity of the system recently discovered in the MACHO data. This project was supported by the NSF/REU grant AST-0097694 and the Nantucket Maria Mitchell Association.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.