Binaries with Mass Ratios Near Unity: The First BVRI Observations, Analysis and Period Studies of TX Canis Minoris and DW Canis Minoris

摘要

CCD BVRI light curves of TX CMi and DW CMi were taken in 2020 on 20, 21 January, 22, 23 February, and 4 April with the 0.81-m reflector of Appalachian State University by Daniel Caton, Ronald Samec and Danny Faulkner. Six times of minimum light were determined from our present observations of TX CMi. 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. Eight times of minimum light were determined for DW CMi and thirty-five total times of minimum light were included in the 19.3-year period study. The period is weakly decreasing with a quadratic term of -1.9 × 10~(-11). This could be due to mass transfer to M_1 (q = M2/M_1) for DW CMi. A Wilson-Devinney (W-D) analysis of TX CMi reveals that the system is a W UMa binary with a mass ratio near unity, q ~1.00. Its Roche Lobe fill-out is ~10%. One spot was needed in the modeling. The temperature difference of the components is only ~90 K, so the stars are nearly twins, with the secondary component the slightly cooler one. The inclination is high, 86.9 ± 0.1°. A W-D analysis reveals that DW CMi is a W-type W UMa binary a mass ratio near unity, q ~1.1. Its Roche Lobe fill-out is ~10%. One weak spot was needed in the modeling. The temperature difference of the components is T_2 - T_1~260 K, making the binary of W-type.