Analyses of the Short-Period Cepheid SU Cassiopeiae

Abstract

Baade-Wesselink analyses of this important Galactic classical Cepheid provide new values for the radius, luminosity, distance, and mass and show SU Cas likely to be pulsating in the first overtone. Application of a modified Baade-Wesselink technique and the maximum likelihood method, which we have previously applied to δ Scuti–type variables, yield values of = 33.0 ± 1.1 R⊙, L = 1536 ± 291 L⊙, = -3.28, r = 486 ± 52 pc, mass (from the Baade-Wesselink radius), M = 6.5 ± 0.6 M⊙ (assuming first-overtone pulsation), and evolutionary mass, Mev = 5.5 ± 0.3 M⊙. The results are consistent with the Hipparcos satellite parallax, 2.31 ± 0.58 mas (433 pc), providing further support for overtone pulsation of SU Cas. In the course of the analyses, a modification to the maximum likelihood method, devised by one of us (W. J. F. W.), is presented as an alternative to the modifications of Laney & Stobie and Coulson, Caldwell, & Gieren.