Photometric and spectral observations of two W UMa stars with periods of one third of a day

Photometric and spectral observations of the W UMa binaries NSVS 254037 and V505 Lac with periods of around 8 hr are presented. The simultaneous light curve and radial velocity curve solutions revealed that their components are of G spectral type. The two targets undergo partial eclipses. They both have overcontact configurations of W subtype with fill-out factor f approximate to 0.1. The derived parameters of NSVS 254037 are: mass ratio q = 2.42; orbital inclination i = 67.1 degrees; temperatures T-1 = 5800 K and T-2 = 5585 K; masses M-1 = 0.47 M and M-2 = 1.15 M; radii R-1 = 0.72 R and R-2 = 1.07 R; luminosities L-1 = 0.53 L and L-2 = 1.0 L; equatorial velocities V-1 = 89 km(-1) and V-2 = 146 km(-1); and distance d = 175 pc, almost the same as those of GAIA(DR2). The derived parameters of V505 Lac are: mass ratio q = 2.53; orbital inclination i = 57.3(0); temperatures T-1 = 5,600 K and T-2 = 5,166 K; masses M-1 = 0.38 M and M-2 = 0.97 M; radii R-1 = 0.69 R and R-2 = 1.04 R; luminosities L-1 = 0.41 L and L-2 = 0.68 L; equatorial velocities V-1 = 106 km(-1) and V-2 = 129 km(-1); and distance d = 117 pc, smaller than those of GAIA by 19%. Thus, NSVS 254037 and V505 Lac turned out similar not only in periods and magnitudes but also in mass ratios, radii, and fill-out factors.