Abstract
Abstract We present X-ray light curves of Cygnus X-3 as measured by the recently launched AstroSat satellite. The light curve folded over the binary period of 4.8 hr shows a remarkable stability over the past 45 years and we find that we can use this information to measure the zero point to better than 100 s. We revisit the historical binary phase measurements and examine the stability of the binary period over 45 years. We present a new binary ephemeris with the period and period derivative determined to an accuracy much better than previously reported. We do not find any evidence for a second derivative in the period variation. The precise binary period measurements, however, indicate a hint of short-term episodic variations in periods. Interestingly, these short-term period variations coincide with the period of enhanced jet activity exhibited by the source. We discuss the implications of these observations on the nature of the binary system.
Highlights
Cygnus X-3 is an enigmatic X-ray binary
Singh et al (2002) have presented the binary ephemeris of Cyg X-3 based on IXAE-PPC data obtained in 1999, RXTE-allsky monitor (ASM) data up to 2001, and other archival pointed observations in the 1994–1998 period along with the binary arrival times reported in the literature
Near the end of the mission, the ASM had even sparser monitoring, and the length segment of the data sets was taken to be of 200 days
Summary
P. Singh , Manojendu Choudhury , S. Received 2016 September 27; revised 2017 September 19; accepted 2017 September 20; published 2017 November 8
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