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Astronomy Colloquium
Blue Stragglers, Blue Lurkers and Stars that Go Bump In the Night
Date: Thursday, February 9th
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Robert Mathieu, University of Wisconsin - Madison
Abstract: A substantial fraction of evolved late-type stars in the Milky Way have
evolved along alternative stellar evolutionary paths in binary systems, both
in star clusters and in the field. As a case in point, in the 4-Gyr open
cluster M67, 25% of the evolved stars do not lie on the single-star
evolutionary isochrone. Thus, understanding these alternative stellar
evolutionary paths are essential to understanding stellar evolution, and to
correctly interpret ensemble studies of stars in the Milky Way.

Today, blue stragglers are seen as the most evident part of a much larger
population of evolved stars that do not fall on a classical single-star
evolutionary path. Indeed recently this population has suddenly grown
further to include a population of such stars lurking within main sequences.
All of these stars trace major alternative pathways of stellar evolution.
They are not anomalous.

Over the last decade observations have shown that most of these stars are
themselves binary stars. Relatedly, theory has argued that they likely form
from an array of processes within binary stars, including mass transfer,
mergers, collisions, and rapid rotation. I will tell of this discovery
journey through the landscape of rich open clusters.
Host: Ke Zhang
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