Speaker
Description
The initial-final mass relation of white dwarfs plays an important role across astrophysics. In a recent analysis of a few carbon-oxygen white dwarfs in intermediate-age open clusters of the Milky Way we identified a kink in the initial-final mass relation, located over a range of initial masses, 1.65 ≲ Mi/Msun ≲ 2.10, which unexpectedly interrupts the commonly assumed monotonic trend. The kink's peak in white dwarf mass of about 0.70-0.75 Msun is produced by stars with Mi ≈ 1.8-1.9 Msun, whereas these final masses are typically associated to Mi~3.0-3.5 Msun. We interpret the kink as the fingerprint of carbon star formation and the modest outflows produced as long the carbon excess remains too low to produce dust grains in sufficient amounts. Under these conditions the mass of the carbon-oxygen core can grow more than is generally predicted by stellar models. In a new systematic follow-up investigation, based on GAIA data, we examine the population of asymptotic giant branch stars, so far largely neglected, that appear in the fields of intermediate-age and young open star clusters. Thanks to GAIA, for the for the first time we identify 49 AGB star candidates, brighter than the tip of the red giant branch, with a good to high cluster membership probability. Among them, we find 19 TP-AGB stars with known spectral type: 4 M stars, 3 MS/S stars, and 12 C stars. By combining observations, stellar models, and radiative transfer calculations that include the effect of circumstellar dust, we characterize each star in terms of initial mass, luminosity, mass-loss rate, core mass, period, and mode of pulsation. The information collected helps us shed light on the TP-AGB evolution at solar-like metallicity, placing constraints on the third dredge-up process, the initial masses of carbon stars, stellar winds, pulsation, and the initial-final mass relation.
| Session | Stellar evolution |
|---|
