RHO Cassiopeiae: A hyperbright radial pulsator?
These data of high resolution in velocity and time are conveniently interpretable in terms of classical radial pulsation of a supergiant photosphere. Based on spectra taken at McDonald during a 1400-days long interval, we infer a dominant quasiperiod of 520 days for Rho Cas with a formal error of less than 10%. Since this period is significantly longer than the radial fundamental mode predicted theoretically (see Sheffer and Lambert 1986, Lovy et al. 1984) this supergiant may well be on its way toward the blue side of the HRD following the end of its reddest evolutionary phase. Rho Cas is predicted to become a WR star within 7000 years. This established radial pulsation behavior of a Ia-0 yellow super-giant hints at the possible existence of a class of radial pulsators at the top of the HRD. Another similar supercepheid may be HR8752, but its behavior is more difficult to interpret (Sheffer and Lambert 1987).
KeywordsRadial Pulsation Radial Velocity Curve Systemic Velocity Equilibrium Radius Blue Side
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