Massive single star evolution: A comparison with observations

A study of K i 7699 Å and related shell lines during the recent eclipse of ϵ Aurigae

“…For high-mass F0Ia star, by the time it evolves for third dredge up and s-process overabundance to occur, carbon burning will takes place and it will become a Supernova (Iben & Renzini 1983). During the stable evolution of massive stars third dredgeup and s-process nucleosynthesis does not occur (Maeder 1993, Martins 2014).…”

Use of Red Supergiant Spectral Features as Age Indicators in Starburst Regions

“…Geneva models referred as standard (Schaller et al 1992;Schaerer et al 1993aSchaerer et al , 1993b assume moderate overshooting of the convective core and use empirical relations for expressing mass-loss rate (Ṁ ) for different masses at different metallicities. There are known to be difficulties in explaining all the observables with one set of assumptions (Maeder 1994;Langer & Maeder 1995). Since our interest here is to compute quantities related to RSGs, we looked for those tracks that correctly reproduce the observed ratios of blue to red supergiants (B͞R).…”

“…They found that only clusters with an age 110 Myr have CaT equivalent widths greater than 6 Å; the older clusters have values around 4 Å. However, their observed relation has only limited use in estimating the age of starburst regions owing to the fact that the evolutionary history of massive stars, and hence the presence of RSGs, is a strong function of metallicity (Maeder 1991) and that starbursts are found in a wide range of metallic environments. Thus, a quantitative interpretation of the observed equivalent widths in starbursts requires studies of the evolutionary behavior of starbursts at different metallicities.…”