The Search for Acoustically-Driven Mass-Loss in Evolved Stars

Details The Search for Acoustically-Driven Mass-Loss in Evolved Stars The Search for Acoustically-Driven Mass-Loss in Evolved Stars

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.3603s&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #36.03; Bulletin of the American Astronomical Society, Vol. 24, p.1175

Astronomy and Astrophysics

Astronomy

1

Scientific paper

Recent ab-initio calculations of stochastic stellar wind models by Cuntz (1992 in Cool Stars VII, ASP Conf. Ser. 26, p.383) have proven remarkably robust in predicting observed chromospheric flow patterns including possible variabilities with time in selected cool, evolved stars. The calculations solve the equations of hydrodynamics using the method of characteristics and assume: (i) saw-tooth shock wave profiles, and (ii) wave periods were changed stochastically while keeping the wave amplitudes constant (see Cuntz 1990 Ap.J. 349, p.141). Among the results of fitting chromospheric flow velocities is the implication that the permitted range of acoustic wave periods for a given star is constrained. We made use of the IUE satellite during August and September 1992 to repeatedly observe two stars, the yellow giant Aldebaran (K5 III) and the red supergiant, Betelgeuse (M2 Iab), in order to sample variations in their atmospheres on timescales of ~ 10(4) to ~ 10(6) seconds, which bracket the predicted mean acoustic wave periods for these objects. In particular, we obtained deep exposures in order to measure density-sensitive line ratios within the C II] intercombination features near 2325A (cf. Lennon et al. 1985 Ap.J. 294, p.200) to test the hypothesis that density fluctuations could be measured as a consequence of these acoustic waves. The results of these observations will be presented and discussed in terms of the number and amplitude of acoustic waves contributing to chromospheric heating and mass loss from these stars, as well as the wave origins in the evolving oscillatory structure of these stellar interiors. We are pleased to acknowledge IUE--NASA grant NAG5-2103 for partial support of this effort.

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