Astron. Astrophys. 346, L73-L75 (1999)

1. Introduction

Cataclysmic variables are interacting binaries where a white dwarf and a red dwarf orbit each other within a few hours. Line emission from the red star is now regularly detected (Harlaftis and Marsh 1996, and references therein). During outburst of the eclipsing dwarf nova IP Peg, irradiation from the hot central regions of the disc is most likely responsible for the line emission located on the red star (Marsh and Horne 1990). During quiescence, H line emission from the red star of IP Peg is transient and its origin is unresolved (Harlaftis et al. 1994). The fast rotation of the red stars in cataclysmic variables and the regular irradiation of their atmosphere by the hot accretion disc present a physical situation which may affect, in the long term, the atmospheric stratification of the companion star and its subsequent evolution. Techniques for mapping either the surface of cool single stars from the absorption lines (Cameron 1999) or the surface of the red star in cataclysmic variables from the emission lines (Marsh and Horne 1988; Rutten and Dhillon 1994) have been developed. These techniques can be used in probing the ionization structure of the upper atmosphere of the red star. Here, we report on spectrophotometric observations of IP Peg, obtained with the 2.5m INT at La Palma, during maximum of the November 1996 outburst, which were aimed to probe the structure of the, recently discovered, spiral arms in the disc of IP Peg (Harlaftis et al. 1999). As a by-product of the observations, we discover metal lines in emission from the secondary star.

© European Southern Observatory (ESO) 1999

Online publication: June 17, 1999
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