1995A&A...301..135M

We present a new spectroscopic orbit for the Algol-type eclipsing binary system TX UMa (HD 93033, P=3.0632 days, α(2000.0)=10 45 20.45, δ= +45 33 58, B8V + G0III-IV, V=7.06-8.76). We find : m₁ sin³i=4.67±0.15M_☉, m₂ sin³i=1.15±0.04M_☉, (a_p+a_s)sin i=15.95 ±0.23R_☉, m₁/m₂=4.04±0.10. This is the first direct measure of the mass ratio for this system and is appreciably different from previous estimates of this quantity (∼3.2) estimated from solutions of the light curves of TX UMa. We ascribe this difference to the large colour changes during the deep primary eclipse which introduce variations in the broad band fluxes that are poorly modeled by the monochromatic fluxes predicted by light curve synthesis codes. We have therefore solved the BV light curves of Koch (1961) excluding the central portions of primary eclipse. The solutions of the light curves have been used to correct the spectroscopic orbit for non-Keplerian effects and to derive absolute parameters for TX UMa as follows: M₁=4.76±0.16M_☉, M₂=1.18±0.04M_☉, R ₁=2.825±0.04R_☉, R ₂=4.24±0.07R_☉, log(L₁/L_☉)= 2.30±0.04, log(L₂/L_☉)= 1.17±0.065. Comparison of TX UMa with non-conservative case B evolution models of De Greve (1993) suggests that the system evolved from an initial mass ratio ≲0.6. However, the orbital period of TX UMa is more than 2 days shorter than any of the model systems, and the observed secondary luminosity of order 10 times less than a model star of the same mass during the slow mass transfer phase.