CE 315: a new interacting double-degenerate binary star

Abstract

We present spectroscopic observations of object CE 315 revealing a blue continuum with strong emission lines. Most of the detected lines are identified with He I or He II in emission, with a handful of faint lines of nitrogen. Notable is the complete absence of hydrogen lines. The He lines exhibit triple-peaked profiles with remarkably broad widths of similar to 2000 km s(-1) (FWZP). The observations show that CE 315 is an interacting binary system with an orbital period of 65.1 +/- 0.7 minutes and a mass ratio of 0.022. We conclude that the most likely scenario for this object is that of an accreting similar to0.77 M. white dwarf with a similar to0.017 M. helium white dwarf as mass donor.