AAVSO: American Association of Variable Star Observers

CCD Photometry, Light Curve Modeling and Period Study of V1073 Herculis, a Totally Eclipsing Overcontact Binary System

Volume 49 number 2 (2021)

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Kevin B. Alton
Desert Blooms Observatory, 70 Summit Avenue, Cedar Knolls, NJ 07927; kbalton@optonline.net
John C. Downing
La Ventana Observatory, 28881 Sunset Road, Valley Center, CA 92082; johndowning2014@outlook.com

Abstract

Precise time-series multi-color (BVIc) light curve data were acquired from V1073 Her at Desert Blooms Observatory (DBO) in 2020 and La Ventana Observatory (LVO) in 2021. New times of minimum from data acquired at DBO and LVO along with other eclipse timings extracted from selected surveys and the literature were used to generate an updated linear ephemeris. Secular analyses (eclipse timing differences vs. epoch) revealed changes in the orbital period of V1073 Her over the past 22 years. Along with an apparent increase in the orbital period, the residuals after a parabolic fit of the data indicated that there was an underlying sinusoidal-like variability. This behavior suggests the putative existence of a third gravitationally bound object or cycles in magnetic activity, both of which are addressed herein. Simultaneous modeling of multicolor light curve data during each epoch was accomplished using the Wilson-Devinney code. Since a total eclipse is observed, a unique photometrically derived value for the mass ratio (qptm) could be determined which subsequently provided initial estimates for the physical and geometric elements of V1073 Her.