Messages from the Core: Excited Gravity Modes in the Nearby Blue Supergiant Star Rigel (\beta Ori)

TL;DR

This study identifies multiple stable gravity-dominated oscillation modes in the nearby supergiant star Rigel, revealing insights into its internal structure and stellar evolution through extensive observational data.

Contribution

The paper reports the detection of 19 significant oscillation modes in Rigel, including the first identification of gravity-dominated mixed-modes excited by the -mechanism.

Findings

Detection of 19 significant oscillation modes in Rigel.

Identification of gravity-dominated mixed-modes.

Oscillation periods range from 75 days to 1 day.

Abstract

Rigel is a bright nearby B8 Ia supergiant star. We observed Rigel for 27.7 days with the MOST satellite and monitored it's optical spectrum for over 6 years. Radial velocity (RV hereafter) curve manifestly calls for tens of modes for prewhitening. We conservatively report on the first 19 significant modes to avoid misdetection of aliases. The variability periods range from about 75 days down to a day. All radial modes are stable. We speculate the presence of gravity-dominated mixed-modes excited by \epsilon-mechanism from the Hydrogen burning shell on top of He burning core.