Analysis of dual band and survey photometry of two low mass ratio contact binary systems

The study presents photometric analysis of the completely eclipsing contact binary systems TYC 8351-1081-1 and ASAS J210406-0522.3. TYC 8351-1081-1 is an extremely low mass ratio (q= 0.086) system with a high degree of contact (f= 0.66) while ASAS J210406-0522.3 is found to be in marginal contact (f= 0.08) with a relatively low-mass ratio of 0.272. There is good thermal contact in both systems with only a small difference in the temperature of the components. The systems have been observed by a number sky surveys over the past 20 years. We compare the light curve solutions from up to three of these surveys and find that survey photometric data manually analysed is robust and yields results comparable to dedicated ground-based photometry. There is evidence of significant luminosity transfer from the primary to the secondary, on the order of 0.5L⊙ for TYC 8351-1081-1 and 0.06L⊙ for ASAS J210406-0522.3. There appears to be no change in the period of either system over the past 20 years and theoretical angular momentum loss is below current measurement threshold in both cases. We also show that the mass ratio and separation are well above the theoretical values for orbital instability in both cases. As would be expected, the density of the secondary components is significantly higher relative to the primary.