The pre-cataclysmic binary RR Caeli revisited⁽¹⁾

Spectroscopy and light curve synthesis

Albert Bruch

Laboratório Nacional de Astrofísica, CP 21, BR-37500-000 Itajubá - MG, Brazil

Abstract:

Time resolved spectroscopic observations of the pre-cataclysmic binary RR Cae in the red permit to measure the radial velocity curve of the late type secondary star and of the H_alpha emission component. The latter is not due to illumination of the secondary by the white dwarf as in other pre-cataclysmic binaries but is intrinsic to the late type star. The phasing of the radial velocity curve enables an improvement of the orbital period. Although radial velocity measurements of the white dwarf primary are still missing the present observations together with a re-analysis of previous photometric measurements with the Wilson-Devinney light curve synthesis routine permit the determination of many system parameters which constitute an improvement over previous determinations by Bruch & Diaz (1998). The component masses are found to be 0.467 M_solar and 0.095 M_solar for the primary and the secondary, respectively. The radius of the latter is at 0.189 R_solar considerably larger than expected for such a low mass star, possibly as a consequence of a previous common envelope phase. An orbital eccentricity, although strongly suggested by the shape of the light curve, is not supported by the radial velocity curve. RR Cae is an eclipsing binary with two spectral line systems, enabling the direct measurement of the component masses. This is of particular importance for the red dwarf secondary which is of later spectral type and probably of lower mass than any other known star for which such measurements are possible.

Stars: variables: other - Stars: binaries: eclipsing - Stars: individual: RR Cae