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Observations, Analyses and 61 Year Period Study of the Solar Type Binary, TX CMI With a Mass Ratio Near Unity

Presentation #128.01 in the session “Understanding the Stars by Watching Them Dance”.

Published onJan 11, 2021
Observations, Analyses and 61 Year Period Study of the Solar Type Binary, TX CMI With a Mass Ratio Near Unity

CCD, BVRI light curves of TX CMi was taken on 20, 21, January, and 22, 23 February, and 4 April, 2020, at the Dark Sky Observatory, North Carolina with the 0.81-m reflector of Appalachian State University by Daniel Caton, Ronald Samec, Danny Faulkner, Jacob Ray, Riley Waddell, and Davis Gentry. The variability of TX CMi was discovered by Hoffmeister (1930). It was classified as an EB-type variable with a maximum V magnitude of 13.461 by Gessner (1966) and an EW-type by the All Sky Automated Survey. Six times of minimum light were determined from our present observations, which include three primary eclipse and three secondary eclipses. Fifty-five total times of minimum light were included in the 61 year period study. From these we determined that the period for TX CMi is increasing. The quadratic ephemeris follows: JD Hel Min I = (2458869.64764 ± 0.00062) d + (0.3892192001 ± 0.0000000658) × E + (0.000000000027 ± 0.000000000001) × E2.

This could be due to mass transfer to M1 (the mass ratio, q = M2/M1). A Wilson-Devinney (W-D) analyses reveals that the system is a W UMa binary (EW-type) with a mass ratio near unity. q ~ 1.00 (star 1 may be very slightly more massive). Its Roche Lobe fill-out is ~10%. One spot was needed in the modeling, a northern, 15 degree latitude, 20 degree radius, spot with a t-fact of 0.78 on the primary component. The temperature difference of the components is only ~90 K, so the stars are nearly twins, with the secondary component as the slightly cooler one. The inclination is high, 86.9 ± 0.1°, but not resulting in a time of constant light but rather a “V” shaped minima due to the nearly equal radii of the components.


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