Post Common Envelope Pre-Cataclysmic and Cataclysmic Variable Binaries

by Sing, David Kent.

Extensive photometric and spectroscopic observations have been obtained for the binary HS1136+6646, a newly formed post-common envelope binary system containing a hot ?DAO.5 primary and a highly irradiated secondary. H1136+6646 is the most extreme example yet of a class of short period systems containing a hot H-rich white dwarf with a K-M companion. An orbital period of 0.83607 ± 0.00003 days has been determined through the phasing of radial velocities, emission line equivalent widths, and photometric measurements spanning a range of 24 months. Radial velocity measurements yield an amplitude of KWD =69±2 kms?1 for the white dwarf and KK7V = 115 ± 1kms?1for the secondary star. Photometric measurements revealed a low amplitude modulation with a period of 234 minutes, associated with the rotation of the white dwarf. The white dwarf is estimated to have an effective temperature and gravity of ?100,000 K and log g?8.29 respectively, indicating the binary system is the second earliest post-CE objects known, having an age around 6.4x105 years. Indications are that the secondary star is overly luminous for its mass. IalsopresentFUSE observations of the magnetic cataclysmic variable V405 Aurigae. Together with four other DQ Her type binaries, V405 Aur forms a small subclass of intermediate polars which are likely to evolve into low magnetic field strength polars. The FUSE spectrum exhibits broad O VI and C III emission-lines as well as a narrow O VI emission-line component which likely forms near the white dwarf surface in an optically thin gas. Radial velocity measurements restrict any orbital modulation to a very low amplitude (KWD =2.5 ± 0.5 km s?1) indicating that the binary system is at low inclination. Recent photometric and spectroscopic observations have revealed J0644+3344 to be a bright, deeply eclipsing cataclysmic variable binary with a 6.46488± 0.00024 14 hour period. Although the nature of the hot component is not presently clear, J0644+3344 is one of the brightest eclipsing nova-like cataclysmic variable system yet. As such, the possibility exists for an unambiguous determination of the masses and temperatures of both components in future studies. 15