Astron. Astrophys. Suppl. Ser. 136, 27-33
Ö. Çakirli - A. Devlen
Ege University Science Faculty, Astronomy and Space Science Department, 35100 Bornova Izmir, Turkey
Received May 25; accepted November 17, 1998
New UBVR light curves of the eclipsing binary HW Vir have been obtained. All the
published times of primary and secondary eclipses have been collected. By adding the
new times of the eclipses obtained by us, the general behavior of the O-C
changes has been revealed. The updated O-C change seems to show a cyclic
character. This behavior may be the result of whether rotation of the apsis
connecting the star's centers or revolution of the couple around a third
body. The former has been excluded due to the fact that the O-C values of primary and
secondary eclipses show similar variation, i.e., not 180
out of
phase. Therefore the O-C changes have been analysed under the assumption of
the light-time effect. The period of revolution around the third body was
found to be 19 years. The time span following the discovery of eclipsing nature of the
system covers 69 percent of the period predicted. The B, V and R light curves
have been analysed by the WD code and the physical parameters of the
components were obtained. The hotter, primary component is an sdB star
with a temperature of about 36 000
K, and the cooler one is a late-type main sequence star with a temperature of
3300 K. The physical parameters derived for the secondary component are in
accordance with the parameters of the theoretical models. This analysis indicates
that the low mass, cooler secondary does not fill its critical Roche lobe.
Therefore, mass accretion from the cool main sequence star to the hot sdB
primary is not yet expected.
Key words: stars: HW Vir -- binaries: eclipsing -- cataclysmic variables
Copyright The European Southern Observatory (ESO)