DX Cygni: A triple system with mass transfer

A dozen of new precise times of eclipses were measured for the eclipsing binary DX Cygni as a part of our long-term observational project for studying neglected eclipsing binaries with a short orbital period. Based on a current $O-C$ diagram, we found for the first time that its period is increasing ($dP/P=1.68\times {10}^{-7}$ day/years) and that times of minima show also significant cyclical changes with a period of about 16 years, caused very probably by a third body orbiting the eclipsing pair. The minimal mass of this companion is 0.49 M_⊙. The light curve solution in Phoebe results to the typical Algol-type semidetached configuration where the secondary fills its Roche lobe. The temperature of primary component was fixed to $T_1=5300$ K according to its spectral type, which gives us $T_2=3330\pm 20$ K for the secondary. The photometric mass ratio was estimated $q=0.504\pm 0.012$. We also compare orbital parameters of selected known Algol-type eclipsing binaries with proven mass transfer and a third body.     

First comprehensive study of W-type W UMa eclipsing binary V1036 Her

CCD photometry of the eclipsing binary system V1036 Her was performed using Johnson V filter in Dr. Mojtahedi Observatory of the University of Birjand during July-August 2017 and July 2018. Moreover, the spectroscopy of the system was carried out by TRES during April 2018. A mass ratio of $3.07\left(27\right)$is obtained and an initial effective temperature of 5500 was suggested. For the first time, the relative and absolute parameters of the system are determined by analyzing the light curve and radial velocity data. The results indicate that V1036 Her is a W-subtype W UMa system with a degree of overcontact of 22%. The analysis of the period change shows that the period of the system changes with the rate of $\dot{P}=2.23\left(4\right)\times {10}^{-7}\text{day}/\text{year}$. With the assumption of the system mass conservation, a mass transfer rate from the primary to the secondary component of ${\dot{m}}_1=1.00\left(3\right)\times {10}^{-7}{M}_{\odot }/\mathit{year}$ is probable. Additionally, a periodic behavior with a period of about 10 years is observed in the O-C curve, which predicts the possibility of a third body with a minimum mass of $0.14\left(1\right)M_{\odot }$.