AAS 207th Meeting, 8-12 January 2006
Session 186 Eclipsing Binaries
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[186.06] Photometric Observations of the low mass Eclipsing Binaries GU Boo and TrES-Her0-07621 from Mount Laguna Observatory

P. A. Rosenfield, L. Huk, D. Garcia, C. Downum, P. B. Etzel, J. A. Orosz (San Diego State)

Low mass double-lined eclipsing binaries are of general interest because precise masses and radii can be derived for the component stars, and these data can in turn be used to test evolutionary models on the lower main sequence. The low mass double-lined eclipsing binaries GU Boo and TrES-Her0-07621 were observed in several bandpasses from the Mount Laguna Observatory (MLO) 2005 May - June with the goal of obtaining precise light curves that can be used to derive accurate radii.

Lopez-Morales & Ribas (2005) present light curves of GU Boo covering both eclipses and radial velocity curves for each component and derive component masses and radii accurate to 1.3% and 2.3%, respectively. Their light curves were not symmetric about the primary eclipse, and Lopez-Morales & Ribas modelled the asymmetry using two dark spots on the primary. Our light curves of GU Boo from MLO show only a slight asymmetry, which indicates the spotted region is much smaller. The radii we derive for the component stars are consistent with the measurements of Lopez-Morales & Ribas, showing that the presence of large star spots did not lead to any systematic errors in the derived radii.

TrES-Her0-07621 was discovered by the Trans-Atlantic Exoplanet Survey (TrES, e.g.\ Alonso et al.\ 2004). Creevey et al.\ (2005) obtained radial velocity curves for both components and derive component masses and radii accurate to 0.6% and 13%, respectively. The radii are poorly constrained since the light curve presented in Creevey et al.\ is somewhat noisy. Our light curves from MLO have a high signal-to-noise ratio, but unfortunately only cover the secondary eclipse. We see evidence of a sinusoidal variation in the out-of-eclipse phases (also noted by Creevey et al.). More observations will be needed to cover the primary eclipse and to establish the nature of the out-of-eclipse variation.

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