Enrico Corsaro Service d'Astrophysique, IRFU/DSM/CEA Saclay

Bayesian asteroseismology of Red Giants

Stellar oscillations similar to those of the Sun, observed in thousands of red giants by the space missions CoRoT and Kepler, allow to greatly deepen our understanding about stellar structure and evolution in cool low-mass stars. 

In this talk we highlight the main results coming from more than 1600 oscillation modes extracted from 19 low-mass low-luminosity red giant branch stars observed by Kepler for more than four years. These results represent the largest set of detailed asteroseismic mode measurements ever obtained. 

Starting from an introduction to the new numerical technique implemented in the Bayesian code DIAMONDS, we show how the high-precision measurements of the individual mode frequencies, amplitudes, and linewidths are obtained. We discuss the new correlation obtained between the mode linewidths and the effective stellar temperature of the stars, and the linewidth depression occurring around the frequency of maximum oscillation power. We also show how to characterize the clear acoustic signatures of the helium second ionization zone in the convective envelope of the stars by exploiting DIAMONDS once again, deriving the most precise and accurate values of acoustic radii of the second helium ionization zones currently available for red giants.

The full set of high-quality asteroseismic measurements obtained can be exploited for an intensive testing of the physics used in stellar structure and evolution models, and for refining existing asteroseismic scaling relations. In addition, thanks to the firm detection of rotation in 14 stars of the sample and to the variety of the stellar masses, these measurements are crucial for a detailed study of the internal rotation profiles and of the mechanisms responsible for the angular momentum transport and its evolution from the main sequence phase of the stellar evolution.

This event will not be webcast or recorded.

Date and time: 
Thursday, June 4, 2015 - 10:30am to 11:30am