Evolution of TX CVn from cataclysmic to stationary P Cyg stage.

TX CVn, a star at high galactic latitude, suspected to be a symbiotic variable because its light curve was resembling Z And, has been for thirteen years almost stationary at maximum. A variable P Cyg spectrum with shells ejected at -140 and -325 km 1 is overposed on a less shifted (-20 km s ') metallic line spectrum originating in the photosphere of a late-type star. A third shell revealed by Call-K has probably been slowed down at its present velocity, -90 km 1, by matter ejected in a previous stellar wind phase. The excitation is moderate: no Paschen lines are seen and among ions with high I.P. only hydrogen shows in emission. The large electron density, estimated about 1014 , explains why we do not record forbidden lines. Rather than a symbiotic star TX CVn is therefore correctly classified as a cataclysmic variable of the P Cyg type (see however Herbig's result quoted by Kukarkin et al. 1969). TX CVn resembles in particular the P Cyg systems 17 Lep and AX Mon, this latter indicating, according to computations by Plavec et al. (1973) a binary with an evolving giant component. The recently reached P Cyg stage in TX CVn might represent a phase where one star is just leaving the main sequence. Possible connections with X-ray novae are outlined. Key words: Cataclysmic variables - P Cyg stars - symbiotic stars - composite spectra - X-ray binaries