POLARIZATION OBSERVATIONS OF DQ HER STARS AND OTHER CATACLYSMIC VARIABLES

Linear and circular polarizations are presented for the DQ Her stars FO Aqr, AE Aqr, EX Hya, AO Psc and V1223 Sgr and for 17 other cataclysmic variables. Upper limits (~0.1 per cent in circular) are set to any periodic varia- tions in the polarization for the DQ Her stars. The source of the large periodic intensity variations in some of these stars is investigated in the light of the null results. Cyclotron radiation is ruled out. AE Aqr may be circularly polarized at the 0.05±0.01 per cent level. Previous claims for the detection of circular polarization in HL CMa and V603 Aql are not confirmed. © Royal Astronomical Society.