AAS 195th Meeting, January 2000
Session 76. Geometrically Variable Stars
Display, Friday, January 14, 2000, 9:20am-6:30pm, Grand Hall

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[76.21] X-Ray Activity in Near-Contact Binary Stars

J. S. Shaw (U. of Georgia), E. C. Smith (U. of Texas)

We have conducted an investigation of the x-ray properties of Near-Contact Binary stars using observations from the ROSAT pointed observations. Near-Contact Binaries (NCB's) are a subclass of close binary star systems which are possible evolutionary precursors to W UMa systems. Of the over 150 NCB's known, 36 were in the ROSAT PSPC or HRI field of view for one or more exposures. Fourteen NCB's were detected while the rest are described by upper limits. The mean logarithm of the luminosity (log Lx) of the NCB's observed by the ROSAT was 30.66 ± .2 ergs/s. This value is higher than the average value found in an earlier survey of NCB's in the ROSAT All Sky Survey (RASS) and higher than the average values for A- or W-Type W UMa systems.

Since some NCB's were observed for several long exposures, light curves of five of the detections were made. There is some evidence in these light curves of a periodic variation in their x-ray emission. In general, the maximum x-ray intensity is at 0.25 phase and the minimum at 0.75 phase. We believe this may be due to enhanced x-ray emission near the trailing hemisphere of the cooler component of the sytem.

The author(s) of this abstract have provided an email address for comments about the abstract: jss@hal.physast.uga.edu

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