Stellar Model Analysis of the Oscillation Spectrum of eta Bootis Obtained from MOST

Abstract

Eight consecutive low-frequency radial p-modes are identified in the G0 IV star eta Bootis based on 27 days of ultraprecise rapid photometry obtained by the MOST (Microvariability & Oscillations of Stars) satellite. The MOST data extend smoothly to lower overtones the sequence of radial p-modes reported in earlier groundbased spectroscopy by other groups. The lower-overtone modes from the MOST data constrain the interior structure of the model of eta Boo. With the interior fit anchored by the lower-overtone modes seen by MOST, standard models are not able to fit the higher-overtone modes with the same level of accuracy. The discrepancy is similar to the discrepancy that exists between the Sun's observed p-mode frequencies and the p-mode frequencies of the standard solar model. This discrepancy promises to be a powerful constraint on models of 3D convection.