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

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 = 65.0⁰, temperatures T ₁ = 6016 K and T ₂ = 5726 K, masses M ₁ = 0.43 {M}_⊙ and M ₂ = 1.47 {M}_⊙ , radii R ₁ = 0.74 {R}_⊙ and R ₂ = 1.28 {R}_⊙ , luminosities L ₁ = 0.64 {L}_⊙ and L ₂ = 1.51 {L}_⊙ . The derived parameters of 1SWASP J034501.24+493659.9 are: mass ratio q = 2.378, orbital inclination i = 60.3⁰, temperatures T ₁ = 6514 K and T ₂ = 6494 K, masses M ₁ = 0.275 {M}_⊙ and M ₂ = 0.654 {M}_⊙ , radii R ₁ = 0.693 {R}_⊙ and R ₂ = 1.012 {R}_⊙ , luminosities L ₁ = 0.775 {L}_⊙ and L ₂ = 1.632 {L}_⊙ . 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 {M}_⊙ 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.