AAS 201st Meeting, January, 2003
Session 54. Compact X-Ray Sources
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[54.04] Long-term X-ray variability of Circinus X-1

P. M. Saz Parkinson, E. D. Bloom, D. Tournear, W. B. Focke (SLAC, Stanford University), P. S. Ray, M. T. Wolff, K. S. Wood (Naval Research Laboratory), J. D. Scargle (NASA/Ames Research Center)

We present an analysis of long term X-ray monitoring observations of Circinus X-1 (Cir X-1) made with four different instruments: Vela 5B, Ariel V ASM, Ginga ASM, and RXTE ASM, over the course of more than 30 years. We use Lomb-Scargle periodograms to search for the ~16.5 day orbital period of Cir X-1 in each of these data sets and from this derive a new orbital ephemeris based solely on X-ray measurements, which we compare to the previous ephemerides obtained from radio observations. We obtain dynamic periodograms (both Lomb-Scargle and PDM) of Cir X-1 during the RXTE era, showing the period evolution of Cir X-1, and also displaying some unexplained discrete jumps in the location of the peak power.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.