# Wolf-Rainer Hamann

Massive stars, winds, feedback, gravitational wave progenitors
When Feb 22, 2018 from 02:30 PM to 03:30 PM Colloquium SH Lecture Hall vCal / iCal

Luminous, massive stars play an important role in cosmic evolution. With their stellar winds and strong ionizing radiation, they have a large impact on their environment. The relevant spectral analysis of hot-star spectra requires adequate stellar atmosphere models. We have developed the  Potsdam Wolf-Rayet (PoWR) model atmosphere code for this purpose, and have performed comprehensive analyses for massive stars of various types (Wolf-Rayet, O- and B-type stars) in our, and other nearby galaxies.

The evolution of massive stars is not yet well understood. One key uncertain factor is the mass loss in different evolutionary stages.  With our spectral analyses we constrain the mass-loss rates of massive stars empirically. In addition, we are developing self-consistent hydrodynamical models.

From the results of the spectral analyses we can quantify the feedback in dependence from stellar parameters. At low metallicities,  as in the SMC, very massive stars are obviously internally mixed and hence evolve chemically homogeneously. We have studied young, star-forming clusters and found that a handful of their most massive stars dominate the ionizing radiation and mechanical feedback.

The mass loss rate during a stellar life also determines how much mass is left at gravitational collapse, and also under which conditions a black hole, or even a close pair of black holes, can form with the high masses observed
in the gravitational wave events.