A spectroscopic study of the eclipsing cataclysmic binary star PG0818 + 513 - A puzzling novalike variable

Abstract

Spectroscopic observations of a novalike variable are reported. The emission-line radial velocities yield an orbital period of 0.156 d (= 3.74 hr), in agreement with the eclipse timings of Andronov et al. (1989). The H-alpha emission shows abrupt increases in equivalent width around the eclipse phase; it is not eclipsed as strongly as the continuum. The radial velocities have a pronounced (about 57 deg) phase lag compared to the eclipse. This object may be a somewhat fainter example of a common, but very puzzling, class of luminous novalike variables, which includes SW Sex, DW UMa, V1315 Aql, and PG0027 + 260.