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W. J. Fischer, N. D. Morrison (U. Toledo)
HD 223960, a class A0 Ia supergiant in the Cas OB5 association, is very unusual for its class in having an H\alpha profile with double-peaked emission entirely above the continuum. We analyzed twelve high-resolution échelle spectra obtained in 1993--1995 and in 1999 with the 1-m telescope of Ritter Observatory. Radial velocities were measured for photospheric Si, C, He, Ne, and S lines, and these values were used to determine a center-of-mass radial velocity for the star. The radial velocities of these lines are constant to within ±2 km s-1. There is likewise little variability in the radial velocities of the H\alpha features; however, the ratio V/R varies strikingly from season to season. The present data do not indicate a binary explanation for the double-peaked emission feature. This star has an unusually large projected rotational velocity for its spectral class (Verdugo et al., A&A, 346, 819). Therefore, the double-peaked H\alpha morphology may be caused by rotational flattening of the stellar wind as in the theoretical H\alpha profiles by Petrenz and Puls (A&A, 312, 195). Nevertheless, the V/R variability is a puzzle.
The author(s) of this abstract have provided an email address for comments about the abstract: wfischer@astro.utoledo.edu