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

CCD, BVRI light curves of TYC 2402 0643 1 were taken on 21, 22, and 23 January 2020 at the Dark Sky Observatory, North Carolina with the 0.81-m reflector. The variability of TYC 2402 0643 1 ([GGM2006] 6868894, NSVS 4382530) was discovered in the sky patrol data taken by the ROTSE-I telescope (Gettel, Geske and McKay, 2006). They classified it as a contact variable with a maximum magnitude of V = 11.373 an amplitude of 0.442 Vmag 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: HJD I = 2457870.51294 ± 0.00036 d, HJD II = 2457870.71359 ± 0.00050 and 2457871.51245 ± 0.00078 d. We selected 3 times of low light from parabola fits of ASAS SN observations. From these we determined both linear and quadratic ephemerides, JD Hel Min I = (2457870.5168 ± 0.00518 + (0.399579 ± 0.000012)×E) d (1), JD Hel Min I = (2457870.51339 ± 0.00017d + (0.39959539 ± 0.00000043)×E + (0.00000002050 ± 0.00000000025)×E²) d (2). Thus, from our limited study, the period appears to be increasing. This could be due to mass transfer making the mass ratio (M₂/M₁) increase. Wilson-Devinney analyses reveal that the system is a W-type W UMa binary with a mass ratio that is somewhat extreme, M₂/M₁ = 0.2079 ± 0.0003 (star 1 is the more massive component, M₁/M₂ = 4.8). The total eclipses make this a firm determination. Its Roche Lobe fill-out is ~22%. No spots were needed in the solution, however the V magnitudes at phase 0.75 were 0.022 brighter than at phase 0.25 giving a slight O’Connell effect. The temperature difference of the components is only ~70 K, with the more massive component as the slightly hotter one, so that in the present observations, it is an A-type W UMa Binary (with such a small component difference, this result is likely variable). The inclination is high, 83.4 ± 0.1 deg resulting in a total eclipse. As a result, the primary minimum has a time of constant light with an eclipse duration of 43 minutes. More information is given in this preliminary report.