AAS 201st Meeting, January, 2003
Session 113. Massive Star Winds and Atmospheres
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[113.03U] A Large ROSAT Survey of Time-Variability in O Stars

A. S. Adelman (Bryn Mawr College and Prism Computational Sciences), D. H. Cohen (Swarthmore College, Department of Physics and Astronomy)

Numerous authors have remarked on the lack of significant X-ray time variability in observations of hot stars. This has been taken to be a constraint on both purported wind-shock and coronal models of X-ray production in these stars. We have undertaken the largest yet survey of X-ray properties of O stars in order to quantify the overall X-ray time variability, or lack thereof. We find that of the 61 O stars with high signal-to-noise ROSAT PSPC data sets in the archives, 12 show time variability at or above the 95% confidence level, including several O stars not previously reported on in the literature. We quantify the variability characteristics of these stars and the upper limits on the remainder of the sample, and analyze the results in the context of wind-shock physics and coronal X-ray production.

This work is supported by NASA, under grant NAG5-9461 to Prism Computational Sciences.

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