Friday September 14th: The origin and ages of the most massive stars - how stellar evolution shapes the mass function

Abstract by Fabian Schneider
The stellar initial mass function (IMF) is the distribution of stellar masses at birth and thus governs observable properties of stellar systems, supernova rates and predicts the outcome of star formation. Contrary, the present day mass function (PDMF) is the stellar mass distribution today, i.e. it is given by the IMF and subsequent evolutionary effects changing stellar masses and their frequencies. One way to change stellar masses is by single and binary star evolution which we investigate here to learn from observed PDMFs about the evolutionary status of stellar samples. To that end we model populations of massive single and binary stars with a rapid binary evolution code and follow their mass functions in time. Stellar wind mass loss, mass transfer because of Roche lobe overflow, stellar mergers and rejuvenation shape the PDMF at the high mass end. From this shape it is possible to determine the age of star clusters and to identify the products of binary evolution. The determination of the stellar upper-mass limit and ages of star clusters based on the most massive stars are thus biased by binary interactions. We apply our findings to the PDMFs of the Arches and Quintuplet clusters and find that their most massive stars are probably the rejuvenated remnants of binary evolution. We conclude that binary star evolution must be taken into account to better understand the stellar content and the formation of star clusters.

Restart of the Journal Club this 2012 Fall

The Massive Stars and Starburst Journal Club will restart next week, September Friday 14th at same time (1pm) and at the usual place (CafeCon at STScI)
Our first talk will be "The origin and ages of the most massive stars - how stellar evolution shapes the mass function" by Fabian Scheider (Argelander Institut für Astronomie, Germany)