Optical spectroscopy of DPVs and the case of LP Ara

We present preliminary results of our spectroscopic campaign of a group of intermediate mass interacting binaries dubbed “Double Periodic Variables” (DPVs), characterized by orbital light curves and additional long photometric cycles recurring roughly after 33 orbital periods (Mennickent et al. 2003, 2005). They have been interpreted as interacting, semi-detached binaries showing cycles of mass loss into the interstellar medium (Mennickent et al. 2008, Mennickent & Ko_laczkowski 2009). High resolution Balmer and helium line profiles of DPVs can be interpreted in terms of mass flows in these systems. A system solution is given for LPAra, based on modeling of the ASAS V-band orbital light curve and the radial velocity of the donor star.