Intrinsic S-type AGB stars, periods and masses

S-type AGB stars are an important constraint on this uncertainty as they have C/O ratios between 0.5 and 1, meaning they have only experienced up to a few episodes of TDU. AGB stars are also long-period variable stars, pulsating in low order radial pulsation modes.

In this paper, we estimate the initial masses of a large sample of intrinsic S-type AGB stars, by analysing their visual light curves, estimating their luminosities with Gaia DR3 parallax distances and finally comparing to a grid of detailed stellar models combined with linear pulsation models. We find that the initial mass distribution of intrinsic S-type stars peaks at 1.3-1.4M_{sun}_ depending on model assumptions. There also appear to be stars with initial masses down to 1 solar mass, which is in conflict with current detailed stellar models.