A spectroscopic study of the old nova HR Delphini

A radial velocity curve derived from spectroscopic observations of the old nova HR Del indicates that the currently adopted binary period is too small, the improved orbital period being 0.2141674 d. The measurements and the canonical model for cataclysmic variables yield 0.9 and 0.58 solar masses for the binary components, and an orbital inclination of 41 deg. The spectral type of the secondary is estimated to be near K8, and it is noted that the intensity of the Balmer emission lines and He II 4686 A may vary during the cycle. It is estimated that the Roche lobe of the primary is almost filled by the accretion disk.