MODELING THE GLOBAL OSCILLATIONS O F E P S I L O N ERIDANI David R. Soderblom Space Telescope Science Institute 3700 San Martin Drive Baltimore, Maryland 21218 USA Werner D ppen High Altitude Observatory National Center for Atmospheric Research P.O. Box 3000 Boulder, Colorado 80307 USA ABSTRACT. We have reviewed the observational data for e Eri to derive our best esti- mates of luminosity, radius, temperature, composition, and age, as well as the uncertainties associated with each of these. These quantities are then used in stellar structure models to try to reproduce the global oscillation frequencies observed by Noyes et al. We find that we can reproduce the observed frequencies and splittings at least as well as the computations of Guenther and D marque, yet for significantly different stellar parameters, most notably the age. 1. REVIEW O F T H E OBSERVATIONAL DATA Noyes et al. (1984) have recently reported the tentative detection of global p-mode oscil- lations, akin to the Sun s 5-minute oscillations, on the K2V star e Eridani. Guenther and D marque (1986: G&D) applied stellar structure models to those observations, to reproduce both the observed frequencies and the frequency spacing of the observations. Their results warrant independent verification. Moreover, the fundamental stellar parameters (radius, temperature, luminosity, metallicity, and age) that are necessary inputs to such models have, we believe, values or uncertainties that are rather different from those used by G&D. A full description of our data and results will be published elsewhere; we present here only a brief summary. We began by reviewing the available photometry for e Eri, and found that its magnitudes and colors were much less certain that expected for a well-observed star. Johnson et al. (1966) tabulate individual photometric observations. Using only their best data we derive V = 3.728 0.039, (U - B) = 0.579 0.048, ( - V) ~. 0.885 0.024, and (V - R) — 0.718 0.021. These large uncertainties are not due to starspots or rotational modulation of the colors, because the changes in magnitude and colors are uncorrected. 281 J. Christensen-Dalsgaard andS. Frandsen (eds.), Advances in Helio- and Asteroseismology, 281-284. 1988 by the 1AU. available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900158231 Downloaded from https://www.cambridge.org/core. IP address: 63.141.32.144, on 24 Apr 2020 at 03:52:56, subject to the Cambridge Core terms of use,