Cataclysmic variables from a ROSAT/2MASS selection -I. Four new intermediate polars

Abstract

We report the first results from a new search for cataclysmic variables (CVs) using a combined X-ray (ROSAT)/infrared (2MASS) target selection that discriminates against background active galactic nuclei. Identification spectra were obtained at the Isaac Newton Telescope for a total of 174 targets, leading to the discovery of 12 new CVs. Initially devised to find short-period low-mass-transfer CVs, this selection scheme has been very successful in identifying new intermediate polars. Photometric and spectroscopic follow-up observations identify four of the new CVs as intermediate polars: 1RXS J063631.9+353537 (Porb ≃ 201 min. Pspin = 1008.3408 s or 930.5829 s), 1RXS J070407.9+262501 (Porb ≃ 250 min, P spin = 480.708 s). 1RXS J173021.5-055933 (Porb = 925.27 min, Pspin = 128.0 s), and 1RXS J180340.0+401214 (Porb = 160.21 min, Pspin = 1520.51 s). RX J1730, also a moderately bright hard X-ray source in the INTEGRAL/IBIS Galactic plane survey, resembles the enigmatic AE Aqr. It is likely that its white dwarf is not rotating at the spin equilibrium period, and the system may represent a short-lived phase in CV evolution. © 2005 RAS.