Long-term X-ray Variability of Circinus X-1

Abstract

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 the peak power.

19 pages, 8 figures, Latex

References in corpus (8)

• First Results from the All-Sky Monitor on the Rossi X-ray Timing Explorer
• The Discovery of Broad P Cygni X-ray Lines from Circinus X-1 with the Chandra High Energy Transmission Grating Spectrometer
• Circinus X-1: survivor of a highly asymmetric supernova
• An asymmetric arcsecond radio jet from Circinus X-1
• The Composite Broad Band Spectrum of Cir X-1 at the Periastron: a Peculiar Z-source
• Spectral Evolution of Circinus X-1 Along its Orbit
• HST observations rule out the association between Cir X-1 and SNR G321.9-0.3
• Secular and orbital variability of Cir X-1 observed in optical spectra

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