Optical and infrared light curves of the eclipsing X-ray binary V395 Car = 2S 0921-630

Abstract

We present results of optical and infrared photometric monitoring of the eclipsing low-mass X-ray binary V395 Car (2S 0921-630). Our observations reveal a clear, repeating orbital modulation with an amplitude of about 1 mag in B and V, and a little less in J. Combining our data with archival observations spanning about 20years, we derive an updated ephemeris with orbital period 9.0026 ± 0.0001d. We attribute the modulation to a combination of the changing aspect of the irradiated face of the companion star and eclipses of the accretion disc around the neutron star. Both appear to be necessary as a secondary eclipse of the companion star is clearly seen. We model the B, V and J light curves using a simple model of an accretion disc and companion star and find a good fit is possible for binary inclinations of 82.°2 ± 1.°0. We estimate the irradiating luminosity to be about 8 × 1035ergs-1, in good agreement with X-ray constraints. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.