2021MNRAS.501.4935B

The first multicolour light-curve models and period studies for the totally eclipsing W UMa stars TYC 3700-1384-1, V1511 Her, and V1179 Her are presented. All three stars are A-subtype W UMa stars of spectral type F. The light-curve solutions show that TYC 3700-1384-1 has a moderately low mass ratio of q = 0.182 ± 0.001 and a degree of overcontact of f = 49 per cent. For V1179 Her a mass ratio q = 0.153 ± 0.001 and a degree of overcontact of f = 48 per cent is derived. The solution for V1511 Her is inconclusive, however the mass ratio is expected to be between 0.13 < q < 0.15. The evolutionary status is compared with zero-age main sequence stars taking into account energy transfer from the primary to the secondary component. The primary component of TYC 3700-1384-1 fits well in the main-sequence, while V1179 Her is more evolved. The period study reveals for all three stars a continuously increasing period at a rate of dP/dt = 6.1×10^–7 d yr^–1, dP/dt = 5.0×10^–7 d yr^–1, and dP/dt = 9.6×10^–7 d yr^–1 for TYC 3700-1384-1, V1511 Her, and V1179 Her, respectively. The estimated mass transfer rates derived from these period changes are {dot}M=1.6 ×10^–7 M_☉_ yr^–1 for TYC 3700-1384-1 and {dot}M= 1.9 ×10^–7 M_☉_ yr^–1 for V1179 Her.