AAVSO: American Association of Variable Star Observers

Light Curve Modeling and Secular Analyses of the Totally Eclipsing Overcontact Binary System, V625 Hydrae

Volume 50 number 1 (2022)

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Kevin B. Alton
UnderOak Observatory, 70 Summit Avenue, Cedar Knolls, NJ 07927; kbalton@optonline.net

Abstract

Precise time-series CCD-derived photometric data (BVIc) were acquired from V625 Hya at Desert Blooms Observatory in 2020. An updated linear ephemeris was calculated from sixteen new times of minimum (ToM) produced from these measurements along with thirteen other values from four ground-based surveys and the literature. Secular analyses (observed minus predicted ToM vs. epoch) revealed changes in the orbital period of V625 Hya over the past two decades, suggesting an apparent increase in the orbital period based on a parabolic fit of the residuals. In addition, simultaneous modeling of these multi-bandpass light curve data was accomplished using the Wilson-Devinney code. Since a total eclipse is observed, a photometrically derived value for the mass ratio (qptm) with acceptable uncertainty could be determined which consequently provided estimates for some physical and geometric elements of V625 Hya.