HS 2237+8154: On the onset of mass transfer or entering the period gap?*
School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK
2 Department of Physics, University of Warwick, Coventry CV4 7AL, UK
3 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
4 Institute of Space Applications and Remote Sensing, National Observatory of Athens, PO Box 20048, Athens 11810, Greece
5 Institute of Astronomy and Astrophysics, National Observatory of Athens, PO Box 20048, Athens 11810, Greece
6 Universitäts-Sternwarte, Geismarlandstr. 11, 37083 Göttingen, Germany
Corresponding author: B. T. Gänsicke, Boris.Gaensicke@warwick.ac.uk
Accepted: 15 January 2004
We report follow-up observations of a new white dwarf/red dwarf binary HS 2237+8154, identified as a blue variable star from the Hamburg Quasar Survey. Ellipsoidal modulation observed in the R band as well as the radial velocity variations measured from time-resolved spectroscopy determine the orbital period to be Porb ± 0.08 min. The optical spectrum of HS 2237+8154 is well described by a combination of a ± 1500 K white dwarf (assuming ) and a dM 3.5 ± 0.5 secondary star. The distance implied from the flux scaling factors of both stellar components is ± 25 pc. Combining the constraints obtained from the radial velocity of the secondary and from the ellipsoidal modulation, we derive a binary inclination of and stellar masses of and . All observations imply that the secondary star must be nearly Roche-lobe filling. Consequently, HS 2237+8154 may be either a pre-cataclysmic variable close to the start of mass transfer, or – considering its orbital period – a cataclysmic variable that terminated mass transfer and entered the period gap, or a hibernating nova.
Key words: stars: binaries: close / stars: individual: HS 2237+8154 / stars: novae, cataclysmic variables
Based in part on observations made at the 1.2 m telescope, located at Kryoneri Korinthias, and owned by the National Observatory of Athens, Greece, and with the Isaac Newton Telescope, which is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.
© ESO, 2004