Photopolarimetric observations of the new eclipsing polar CTCV J1928-5001

Abstract

We report photopolarimetric observations of a new eclipsing polar (AM Herculis system) discovered in the Calan-Tololo survey. The photometry and polarimetry are modulated on a period of ~101 minutes. Circular polarization variations are seen from ~-8 to +12 per cent and from ~0 to ~5 per cent in the red and blue parts of the optical spectrum, respectively. Two linearly polarized pulses are detected at orbital phases coinciding with the reversals in the circular polarization. This is consistent with a magnetic field strength of ~20 MG for the white dwarf primary, where accretion takes place at two regions. Both accretion regions are self-occulted by the white dwarf during parts of the orbit. We estimate some of the system's parameters from its eclipses, which we further refine by modelling the polarimetric observations.