AAVSO: American Association of Variable Star Observers

CCD Photometry, Light Curve Modeling, and Period Study of Four Overcontact Binary Systems: EI CMi, NSVS 3092802, V1309 Her, and V958 Mon

Volume 48 number 2 (2020)

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


Precise time-series multi-color light curve data were acquired at Desert Blooms Observatory (DBO) from EI CMi (2018–2019), NSVS 3092802 (2018–2019), V958 Mon (2018), and V1309 Her (2018). Except for V958 Mon, only monochromatic CCD photometric data are available from automated surveys which employ sparse sampling strategies. Each target produced new times of minimum from data acquired at DBO which along with other eclipse timings from the literature and those extrapolated from various sources were used to generate new ephemerides. Secular analyses (eclipse timing differences vs. epoch) revealed changes in the orbital period of each system; related evidence suggests that V1309 Her may be a ternary system. Simultaneous modeling of multicolor light curve data from each target was accomplished using the Wilson-Devinney code. Each system exhibits a total eclipse, therefore 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 each variable system.