Accretion efficiency and mass transfer in two binary star systems
We analyze the accretion properties of two binary star systems: the BY Draconis type variable V1803 Cyg, which is an A component of the binary system 61Cyg and the semi-regular (SR) symbiotic variable NQ Gem. In this aim, we estimate an accretion efficiency in these binaries, based on the relation between luminosity and rate of accretion. We give an appraisal on the currently active mass transfer mechanism between the components in the binaries. This could be relevant to the type of accretion, wind or disc is dominant for each of the objects. A feasible contribution of the accretion rate to the objects’ activity states, as an effect on the luminosity variations is considered. An X-ray variability of NQ Gem in the range of 0.3 – 10keV, with a maximum count rates activity mostly in the hard band part of the energy spectrum, is detected. We compare the results for both objects, according to the features of their different stellar types.