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: 1RXSJ063631.9+353537 (P<SUB>orb</SUB>~= 201min, P<SUB>spin</SUB>= 1008.3408s or 930.5829s), 1RXSJ070407.9+262501 (P<SUB>orb</SUB>~= 250min, P<SUB>spin</SUB>= 480.708s), 1RXSJ173021.5-055933 (P<SUB>orb</SUB>= 925.27min, P<SUB>spin</SUB>= 128.0s), and 1RXSJ180340.0+401214 (P<SUB>orb</SUB>= 160.21min, P<SUB>spin</SUB>= 1520.51s). RXJ1730, also a moderately bright hard X-ray source in the INTEGRAL/IBIS Galactic plane survey, resembles the enigmatic AEAqr. 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.