Asteroseismology of the Nearby SN-II Progenitor: Rigel Part I. The MOST High Precision Photometry and Radial Velocity Monitoring

Abstract

Rigel (beta Ori, B8 Ia) is a nearby blue supergiant displaying alpha Cyg type variability, and is one of the nearest type-II supernova progenitors. As such it is an excellent test bed to study the internal structure of pre core-collapse stars. In this study, for the first time, we present 28 days of high precision MOST photometry and over 6 years of spectroscopic monitoring. We report nineteen significant pulsation modes of SNR>4.6 from radial velocities, with variability time scales ranging from 1.21 to 74.7 days, which are associated with high order low degree gravity modes. While the radial velocity variations show a degree of correlation with the flux changes, there is no clear interplay between the equivalent widths of different metallic and Halpha lines.