HS0139+0559, HS0229+8016, HS0506+7725, and HS0642+5049: four new long-period cataclysmic variables

摘要

We present time-resolved optical spectroscopy and photometry of four relatively bright (V similar to 14.0-15.5) long-period cataclysmic variables (CVs) discovered in the Hamburg Quasar Survey: HS 0139+0559, HS 0229+8016, HS 0506+7725, and HS 0642+5049. Their respective orbital periods, 243.69 +/- 0.49 min, 232.550 +/- 0.049 min, 212.7 +/- 0.2 min, and 225.90 +/- 0.23 min are determined from radial velocity and photometric variability studies. HS 0506+7725 is characterised by strong Balmer and He emission lines, short-period (similar to 10-20 min) flickering, and weak X-ray emission in the ROSAT All Sky Survey. The detection of a deep low state (B similar or equal to 18.5) identifies HS 0506+7725 as a member of the VYScl stars. HS 0139+ 0559, HS 0229+ 8016, and HS 0642+5049 display thick- disc like spectra and no or only weak flickering activity. HS 0139+ 0559 and HS 0229+ 8016 exhibit clean quasi-sinusoidal radial velocity variations of their emission lines but no or very little orbital photometric variability. In contrast, we detect no radial velocity variation in HS 0642+5049 but a noticeable orbital brightness variation. We identify all three systems either as UXUMa- type novalike variables or as ZCam-type dwarf novae. Our identification of these four new systems underlines that the currently known sample of CVs is rather incomplete even for bright objects. The four new systems add to the clustering of orbital periods in the 3-4 h range found in the sample of HQSselected CVs, and we discuss the large incidence of magnetic CVs and VYScl/SW Sex stars found in this period range among the known population of CVs.