AAVSO: American Association of Variable Star Observers

TYC 2402-0643-1: First Precision Photometric Observations and Analyses of the Totally Eclipsing, Solar Type Binary

Volume 48 number 1 (2020)

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Ronald G. Samec
Faculty Research Associate, Pisgah Astronomical Research Institute, 1 PARI Drive, Rosman, NC 28772; ronaldsamec@gmail.com
Daniel B. Caton
Dark Sky Observatory, Physics and Astronomy Department, Appalachian State University, 525 Rivers Street, Boone, NC 28608-2106; catondb@appstate.edu
Danny R. Faulkner
Johnson Observatory, 1414 Bur Oak Court, Hebron, KY 41048; dfaulkner@answersingenesis.org


CCD BVRI light curves of TYC 2402-0643-1 were taken on 21, 22, and 23 January 2020 at the Dark Sky Observatory, Boone, North Carolina, with the 0.81-m reflector of Appalachian State by Daniel Caton. The variability of TYC 2402-0643-1 ([GGM2006] 6868894, NSVS 4382530) was discovered in the sky patrol data taken by the ROTSE-I telescope. It is classified as a contact variable with a maximum V magnitude of 11.373, an amplitude of V = 0.442, and a period of 0.399579 d. Three times of minimum light were determined from our present observations, which include one primary eclipse and two secondary eclipses. We selected three times of low light from ASAS observations and Gettel sent us some ROTSE data. From these we determined a 20-year study and a quadratic ephemeris. Thus, from our study, the period is found to be increasing. This could be due to mass transfer making the mass ratio (q = M2 / M1) decrease. A Wilson-Devinney analysis reveal that the system is an A-type W UMa binary (the hotter component is the more massive) with a somewhat extreme mass ratio, q = 0.2079 ± 0.0003 (star 1 is the more massive, primary component, 1 / q = M1 / M2 = 4.8). Its Roche Lobe fill-out is ~ 22%. No spots were needed in the solution. The temperature difference of the components is only ~70 K, so it is in strong thermal contact. The inclination is high, 83.4 ± 0.1°, resulting in a total eclipse. As a result, the secondary minimum has a time of constant light with an eclipse duration of some 43 minutes.