Echelle-Mepsicron Time-Resolved Spectroscopy of the Dwarf Nova SS Cygni

Abstract

High dispersion time-resolved spectrograms of the dwarf nova SS Cygni, obtained with the Echelle-Mepsicron system, show double peaked emission lines with a complex profile. The intensity of the Hβ line appears to be modulated by the orbital period. Radial velocity measurements of the wings of Hβ and of the absorption line system of the late-type star yield semiamplitude values of K_em = 101 ± 6 km s⁻¹ and K_ab = 151 ± 7 km s⁻¹, respectively. Radial velocity measurements of the blue and red peaks and of the central absorption of Hβ reveal a synchronous movement with the broad wings, although there is some evidence of a narrow component probably associated with a hot spot in the disk or a chromospheric emission line from the secondary star. The Hβ modulation, the double profile and recently discovered UBV light variations support an inclination angle i ~ 50°. The masses of the primary and secondary stars using this angle and the observed semiamplitudes are M_p = 0.60 M_⊙ and Ms = 0.40 M_⊙, respectively. A detailed analysis of the absorption lines reveals a spectral type of K2V.