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A Cessation of X-ray Dipping Activity in X1254-690

Alan P. Smale·Stefanie Wachter
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Abstract

We present results from a campaign of simultaneous X-ray and optical observations of X1254-690 conducted using the Rossi X-ray Timing Explorer and the CTIO 1.5m telescope. We find that the usually-observed deep X-ray dipping is not seen during the times of our observations, with an upper limit of ~2% on any X-ray orbital variation, and that the mean optical variability has declined in amplitude from 0.40+-0.02 mag (in V) to 0.28+-0.01 mag. These findings indicate that the vertical structure on the disk edge associated with the impact point of the accretion stream has decreased in angular size from 17-25 degrees to <10 degrees, and support the suggestions of previous modeling work that the bulge provides 35-40% of the contribution to the overall optical modulation. The average optical and X-ray brightnesses are comparable to their values during dipping episodes, indicating that the mean accretion rate and disk radius remain unchanged.

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Alan P. Smale, Stefanie Wachter. 1999-07-23. A Cessation of X-ray Dipping Activity in X1254-690. https://doi.org/10.1086/308089

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