PREDNASAJUCI / LECTURER :

Theodor Pribulla

(1) Astronomical Institute, Slovak Academy of Sciences,
059 60 Tatranská Lomnica

NAZOV / TITLE :

Minimum mass ratio of contact binaries

ABSTRAKT / ABSTRACT :

Contact binaries with W UMa-type light curves are the closest stellar systems with
non-degenerate components. Both stars in a contact binary are surrounded by a common
envelope that distributes energy and makes the less massive star appear more luminous
compared to a single object of the same mass. Recently, several systems were claimed to
have extremely low mass ratios down to q = 0.024. These claims contradict the so-called
Darwin instability, which leads to a merger and thus should not exist. The determined
mass ratios were obtained solely from photometric observations. TESS data for four
systems are re-analysed using code ROCHE, and it is shown that the published parameters
are very probably affected by strong third light, the absence of multi-colour
observations, and parameter degeneracies. First photometric and spectroscopic
observations obtained with a 80cm telescope in Szombathely (Hungary) and 1.3m telescope
at Skalnate pleso.