Asteroseismology of red giants: Photometric observations of Arcturus by SMEI

Abstract

We present new results on oscillations of the Kl.5 III giant Arcturus (α Boo), from analysis of just over 2.5 yr of precise photometric observations made by the Solar Mass Ejection Imager on board the Coriolis satellite. A strong mode of oscillation is uncovered by the analysis, having frequency 3.51 ± 0.03 μHZ. By fitting its mode peak, we are able to offer a highly constrained direct estimate of the damping time (τ = 24 ± 1 d). The data also hint at the possible presence of several radial-mode overtones, and maybe some non-radial modes. We are also able to measure the properties of the granulation on the star, with the characteristic time-scale for the granulation estimated to be ~0.50 ± 0.05 d. © 2007 The Authors. Journal compilation © 2007 RAS.