New multiband CCD photometry is presented for the eclipsing binary GW Gem; the RI light curves are the first ever compiled. Four new minimum timings have been determined. Our analysis of eclipse timings observed during the past 79 years indicates a continuous period increase at a fractional rate of +(1.2±0.1)×10−10, in excellent agreement with the value +1.1×10−10 calculated from the Wilson-Devinney binary code. The new light curves display an inverse O'Connell effect increasing toward longer wavelengths. Hot and cool spot models are developed to describe these variations but we prefer a cool spot on the secondary star. Our light-curve synthesis reveals that GW Gem is in a semi-detached, but near-contact, configuration. It appears to consist of a near-main-sequence primary star with a spectral type of about A7 and an evolved early K-type secondary star that completely fills its inner Roche lobe. Mass transfer from the secondary to the primary component is responsible for the observed secular period change.
@article{arxiv.0812.4632,
title = {Photometric Properties of the Near-contact Binary GW Geminorum},
author = {Jae Woo Lee and Seung-Lee Kim and Chung-Uk Lee and Ho-Il Kim and Jang-Ho Park and So-Ra Park and Robert H. Koch},
journal= {arXiv preprint arXiv:0812.4632},
year = {2009}
}
Comments
20 pages, including 5 figures and 6 tables, accepted for publication in PASP