Nonradial Pulsation Mode-Typing of 53 Per from the Far-UV

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Session 84 -- Variable Stars
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[84.04] Nonradial Pulsation Mode-Typing of 53 Per from the Far-UV

L. Huang (U. Beijing) and M.A.Smith (CSC/IUE)

Voyager 2 (FUV) spectroscopic observations during January 1991 have been obtained and compared with coterminous optical photometric observations by Huang et al. (1994, ApJ, in press). The ephemeris derived from the optical light curve shows a two-mode solution with frequencies of 0.462 and 0.233 cy~d$^{-1}$. These frequencies are also in good agreement with frequencies derived for 53 Per in the late 1970's and mid-1980's. The FUV results show excellent agreement with the FUV light (1180\AA) and color (1180\AA~- 1585\AA) curves. The UV/visual amplitude implied is 4.6$\pm$1.

On the asssumption that the optical and UV periods arise from nonradial pulsation (NRP) modes, we compare our UV amplitudes with those obtained by linear NRP theory. To make this comparison we have computed wavelength-dependent, limb-darkening integrals from metal line blanketed model atmospheres and used them to evaluate the sources of light variations. We find that the effects of temperature on these modes should be dominant, a prediction verified by the new UV data. We also derive a modal identification $l$ = 2 for the principal mode.

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