Absolute parameters of the newly-identified contact binary star IS Canis Major

This paper presents the results of the first high-resolution spectroscopic observations of the Southern W UMa type system IS CMa. Spectroscopic observations of the system were made at Mt. John University Observatory using a HERCULES fibre-fed échelle spectrograph in September 2007. The first radial velocities of the component stars of the system were determined by using the spectral disentangling technique. The resulting orbital elements of IS CMa are: a1sini=0.0041±0.0001a1sini=0.0041±0.0001 AU, a2sini=0.0135±0.0001a2sini=0.0135±0.0001 AU, M1sin3i=1.48±0.01M⊙, and M2sin3i=0.44±0.01M⊙. The components were found to be in synchronous rotation taking into account the disentangled HδHδ line profiles of both components of the system. The Hipparcos light curve was solved by means of the Wilson–Devinney method supplemented with a Monte Carlo type algorithm. The radial velocity curve solutions including the proximity effects give the mass ratio of the system as 0.297 ± 0.001. The combination of the Hipparcos light and radial velocity curve solutions give the following absolute parameters of the components: M1=1.68±0.04M⊙,M2=0.50±0.02M⊙,R1=2.00±0.02R⊙,R2=1.18±0.03R⊙,L1=7.65±0.60 L⊙L⊙ and L2=1.99±0.80L⊙. The distance to IS CMa was calculated as 87±587±5 pc using the distance modulus with corrections for interstellar extinction. The position of the components of IS CMa in the HR diagram are also discussed: the system seems to have an age of 1.6 Gyr.