Photometric and Spectral Observations of the W UMa Stars NSVS 4161544 and 1SWASP J034501.24+493659.9. GAIA Challenges

Abstract

Photometric and spectral observations of the W UMa binaries NSVS 4161544 and 1SWASP J034501.24+493659.9 with periods of around 8 hr are presented. The simultaneous light-curve and radial-velocity-curve solutions revealed that the two targets have over-contact configurations, and their components undergo partial eclipses. The derived parameters of NSVS 4161544 are: mass ratio q  = 3.377, orbital inclination i  = 65.0 0 , temperatures T 1  = 6016 K and T 2  = 5726 K, masses M 1  = 0.43 and M 2  = 1.47 radii R 1  = 0.74 and R 2  = 1.28 luminosities L 1  = 0.64 and L 2  = 1.51 . The derived parameters of 1SWASP J034501.24+493659.9 are: mass ratio q  = 2.378, orbital inclination i  = 60.3 0 , temperatures T 1  = 6514 K and T 2  = 6494 K, masses M 1  = 0.275 and M 2  = 0.654 radii R 1  = 0.693 and R 2  = 1.012 luminosities L 1  = 0.775 and L 2  = 1.632 . Hence, the masses of the 1SWASP J034501.24+493659.9 components are quite small for the rest global parameters, and their sum of 0.93 is slightly below the lower mass limit of 1.0–1.2 M ⊙ for the contact binaries. The calculated distance of NSVS 4161544 almost coincides with that determined by GAIA . The calculated distance of 1SWASP J034501.24+493659.9 is considerably smaller than the GAIA value that is most likely due to overestimation of the interstellar extinction to this star from the Galactic disk.