Optical and Infrared Light Curves of the Eclipsing X-ray Binary V395 Car = 2S 0921-630

TL;DR

This study presents optical and infrared light curves of the eclipsing X-ray binary V395 Car, revealing orbital modulation, refining its period, and modeling the system to estimate inclination and irradiating luminosity.

Contribution

It provides the first combined optical and infrared light curves, an updated orbital period, and a simple model of the binary system.

Findings

Orbital period refined to 9.0026 days.

Detected secondary eclipse of the companion star.

Estimated irradiating luminosity consistent with X-ray data.

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 one magnitude in B, and V and a little less in J. Combining our data with archival observations spanning about 20 years, 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 disk 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 lightcurves using a simple model of an accretion disk and companion star and find a good fit is possible for binary inclinations of 82.2+/-1.0 degrees. We estimate the irradiating luminosity to be about 8x10^35 erg/s, in good agreement with X-ray constraints.