HEAD 2003 Meeting
Session 17. X-ray Binaries III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[17.23] Long-term X-ray variability of Cir X-1

P. M. Saz Parkinson, D. M. Tournear, E. D. Bloom, W. B. Focke, K. T. Reilly (SLAC, Stanford University), K. S. Wood, P. S. Ray, M. T. Wolff (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 also use the Phase Dispersion Minimization (PDM) technique, as well as FFT analysis, to verify the periods obtained from periodograms. 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 peak power.

Work at SLAC was supported by Department of Energy contract DE-AC 03-76-SFO0515. Basic research in X-ray astronomy at the Naval Research Laboratory is supported by ONR/NRL. This work was also supported by the NASA Applied Information Systems Research Program.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.