Poster abstract details

The SW Sextantis (SW Sex) systems belong to a subclass of cataclysmic variables (CVs) of the novalike type. The CVs are compact binary systems with mass transfer from a low-mass main-sequence or slightly evolved star, the secondary star, to a white dwarf, the primary star. The accretion disk of novalikes is always in a bright state due to the high mass-transfer rate from the secondary, which maintains the disk in a high viscosity regime. From an observational point of view, SW Sex objects are defined by some peculiarities, among which we emphasize: (i) single-peak emission lines, even in systems seen by high inclinations, for which we expect double-peak lines; (ii) lagged radial velocity curve of the emission lines relative to the orbital motion of the white dwarf. Some scenarios are proposed to explain this phenomenology: stream overflow above the orbital plane; disk winds; flared disk and/or magnetic accretion.

We show preliminary results of optical linear and circular polarimetry obtained in Observatory Pico dos Dias (OPD-LNA/MCTI) of a sample of six SW Sex objects: UU Aqr, SW Sex, V442 Oph, V380 Oph, LS Peg, and 1H 0204-023.The existence of non-zero circular polarization can be interpreted as cyclotron emission. This indicates the presence of magnetic fields controlling the accretion near the white dwarf, corroborating the magnetic scenario.