Alternative Pathways of Stellar Evolution in Open Clusters
Bob Mathieu - University of Wisconsin -Madison
Our understanding of the evolution of single stars is one of the great intellectual accomplishments of the past century. Even so, from their beginnings cluster color-magnitude diagrams have shown many stars that do not lie along the main sequences and giant branches. The most famous of these are the blue stragglers, but there are numerous others as well. In fact, as many as 25% of the evolved stars in older open clusters do not fall on single-star isochrones. Rather than being anomalies, these stars represent frequently traveled alternative pathways of stellar evolution. I will review the status of observations, and consequent understanding, of blue stragglers, yellow giants, sub-subgiants and other stars of interest in old open clusters, including recent results from the K2 campaign on M67. Their stories will begin with the rich binary populations among solar-type stars in these clusters. It is inevitable that the evolution of the stars in many of these binaries will be affected by the presence of their companions, and follow alternative stellar evolutionary paths. Their narratives will include both evolutionary processes internal to the binaries and external stellar dynamical influences.
Coffee and Donuts will be served at 2:00pm in 4054 McPherson Lab.