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arXiv · 0812.4632

Photometric Properties of the Near-contact Binary GW Geminorum

Jae Woo Lee·Seung-Lee Kim·Chung-Uk Lee·Ho-Il Kim·Jang-Ho Park·So-Ra Park·Robert H. Koch
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Abstract

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$\pm$0.1)$\times10^{-10}$, in excellent agreement with the value $+1.1\times10^{-10}$ 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.

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Jae Woo Lee, Seung-Lee Kim, Chung-Uk Lee, Ho-Il Kim, Jang-Ho Park, So-Ra Park, Robert H. Koch. 2009-02-23. Photometric Properties of the Near-contact Binary GW Geminorum. https://doi.org/10.1086/597169

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