First science with the Southern African Large Telescope: peering at the accreting polar caps of the eclipsing polar SDSS J015543.40+002807.2

Abstract

We describe briefly the properties of the recently completed Southern African Large Telescope (SALT), along with its first light imager SALTICAM. Using this instrument, we present 4.3 h of high-speed unfiltered photometric observations of the eclipsing polar SDSS J015543.40+002807.2 with time-resolution as short as 112 ms, the highest-quality observations of this kind of any polar to date. The system was observed during its high-luminosity state. Two accreting poles are clearly seen in the eclipse light curve. The binary system parameters have been constrained: the white dwarf mass is at the low end of the range expected for cataclysmic variables. Correlations between the positions of the accretion regions on or near the surface of the white dwarf and the binary system parameters were established. The sizes of the accretion regions and their relative movement from eclipse to eclipse were estimated: they are typically 4°–7° depending on the mass of the white dwarf. The potential of these observations will only fully be realized when low-state data of the same kind are obtained and the contact phases of the eclipse of the white dwarf are measured.