Constraining the internal structure of stars on the asymptotic giant branch
Guillaume Dréau (LESIA, Paris Observatory)
The success of the CoRoT and Kepler space-borne missions has opened a new era for stellar physics. Indeed, thanks to the four-year time series of Kepler, it is now possible to decipher in detail the oscillation spectrum of evolved giants. The information contained in these oscillation spectra, which still needs to be precisely studied for evolved red-giant branch (RGB) and asymptotic-giant branch (AGB) stars, is of major importance to probe the inner stellar structure, which is poorly probed with spectroscopy alone.
In this context, we considered the acoustic modes that develop in stellar interiors and we performed a thorough analysis of the oscillation spectra of ~ 2.000 evolved giants, including RGB and AGB stars. My presentation will focus on the physical differences between RGB and AGB stars. I will highlight the significant differences in the typical signature of the second helium ionisation zone in mode frequencies, which makes a seismic classification between evolved RGB and AGB stars possible. The physical conditions inside those stars will be addressed with stellar evolution and oscillation codes.