V795 HER - AN SW SEX STAR IN THE PERIOD GAP

We present optical photometry and spectroscopy of the nova-like variab le V795 Her. The emission lines exhibit an extremely complex structure consisting of several time-variable emission and absorption component s. We confirm the spectroscopic modulation of 0.1082 d which we attrib ute to the orbital period of the system. The equivalent widths (EWs) o f all the emission lines are strongly modulated on this period, showin g a pronounced minimum around phase 0.5. We associate this minimum wit h the transit of an absorption feature which drives dramatic line chan ges, seen as transient double peaks and P Cygni type profiles. The abs orption depth grows with the excitation level in Balmer and He I lines , but both the He II lambda 4686 and the metallic lines (e.g. C II lam bda 4267 and the Bowen blend) are entirely in emission. The centroid o f the H alpha emission (which is contaminated very little by the absor ption feature) is delayed by 83 degrees with respect to the high-excit ation lines. We assume that the latter trace the orbital motion of the primary, enabling us to define an absolute zero-phase. High-velocity S-waves are clearly observed in all Balmer lines, with amplitudes of a bout 1750 km s(-1) and maximum redshift at about phase 0. However, our high-resolution spectra suggest that these can be separated into two phased components, with gamma-velocities of similar to +/- 750 km s(-1 ) and K similar to 1000 km s(-1), probably formed in accretion columns on the white dwarf. In addition, the H I cores exhibit the presence o f low-velocity (K = 268 km s(-1)) S-waves, roughly phased with their h igh-amplitude partners. On the other hand, our R-band photometry is do minated by flickering with no evidence for modulation with the orbital period nor the previously reported 0.1165-d periodicity. Based on the spectral properties, we propose that V795 Her is a new SW Sex star, o bserved at intermediate inclination. The complex behaviour of V795 Her can be qualitatively explained invoking an intermediate polar scenari o with a synchronously rotating white dwarf.