New BVR photometry of the ultra-short period eclipsing binary HW Vir is presented. The light curves were analyzed with the Wilson-Devinney synthesis method. The primary component is found to be a hot sdB subdwarf with the mass M_1 = 0.5 Modot, radius R_1 = 0.18 Rodot and the effective temperature T_1 = 26000 K. The secondary component with the temperature T_2 = 3250 K, mass M_2 = 0.15 Modot and R_2 = 0.18 Rodot is placed on the H-R diagram close to the main sequence, but is somewhat hotter than typical dM star of the same mass. The illuminated hemisphere of the cool star is heated to the mean temperature of about 9000 K. The hot component is a typical Extended Horizontal Branch star at the beginning of the core helium burning. Its evolutionary status appears to be practically unaffected by close proximity of the cool low-mass companion. The binary HW Vir will most likely become a cataclysmic variable with the period 0.08 days on the time scale of 1.8 billion years.
- Pub Date:
- October 1994
- BINARIES: ECLIPSING;
- STARS: FUNDAMENTAL PARAMETERS;
- STARS: INDIVIDUAL: HW VIR