Search for cataclysmic variables based on the 400d X-ray sky survey.

We present the first results of our search for cataclysmic variables among the point X-ray sources detected in a part of the sky survey with an area of 400 sq. deg. performed on the basis of data from the ROSAT telescope (400d), for which photometric data from the Sloan Digital Sky Survey are also available. The necessary optical observations of the candidates for cataclysmic variables have been carried out with the 1.5-m Russian-Turkish telescope (RTT-150). We show that one of the four investigated objects (400D J0019126+220733) is a cataclysmic variable, two objects are quasars at redshifts z ∼ 2, and the nature of one object remains unclarified; however, we can exclude it from the list of possible candidates for cataclysmic variables: its spectrum contains no characteristic emission features. [ABSTRACT FROM AUTHOR]