AAVSO: American Association of Variable Star Observers

Multi-color Photometry, Roche Lobe Analysis and Period Study of the Overcontact Binary System, GW Bootis

Volume 46 number 2 (2018)

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Kevin B. Alton
UnderOak Observatory, 70 Summit Ave, Cedar Knolls, NJ, kbalton@optonline.net

Abstract

GW Boo is a relatively bright (V-mag ~ 10.2) eclipsing W UMa binary system (P = 0.513544 d) which has surprisingly escaped detailed study since the first monochromatic light curve (LC) was published in 2003. LC data collected in 2011 and 2017 (B, V and Ic) at UnderOak Observatory (UO), produced eight new times-of-minimum for GW Boo which were used along with other eclipse timings from the literature to update the linear ephemeris. Secular variations (P3 ~ 10.5y) in the orbital period suggested the possibility of a gravitationally bound third body. Roche modeling to produce synthetic LC fits to the observed data was accomplished using phoebe 0.31a and wdwint 56a. In order to achieve the best synthetic fits to the multi-color LCs collected in 2011 and 2017 cool spot(s) were added to the Roche model.