Quantitative analysis of the oscillation spectrum of [eta] Bootis

Abstract

We analyze the recent ground-based p-mode oscillation observations of [eta] Boo by Kjeldsen and his collaborators using a large and dense grid of stellar model oscillation spectra parameterized by mass, age, and metallicity. The differences between the model and observed oscillation spectra are quantified by a [subscript X][superscript 2] formulation. Based on the seismic data alone we determine two possible solutions for [eta] Boo’s mass, age, and metallicity. One solution exhibits mode bumping and is within 1 [sigma] of [eta] Boo’s observed luminosity, effective temperature, and metallicity, and the other solution does not exhibit mode bumping and is within 2 [sigma] of [eta] Boo’s observed luminosity, effective temperature, and metallicity. We show how mode bumping (also associated with the terms ‘‘mixed modes’’ and ‘‘avoided crossings’’) can be used to fine-tune the age determination. We also show that the nonadiabatic model frequencies are in better agreement with the observed frequencies than the adiabatic frequencies.