2021JAVSO..49..138S

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 M1 (q = M2/M1) 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 T2-T1 ∼260 K, making the binary of W-type.