PI: M. Virginia McSwain, Yale University, firstname.lastname@example.org
Address: Department of Astronomy, P.O. Box 208101, New Haven, CT 06520-8101
Title: The Evolutionary Status and Disk Variability of Be Stars
Abstract: Be stars are a class of rapidly rotating B-type stars with circumstellar disks that cause Balmer and other line emission. There are three possibile causes for their rapid rotation: they may have been born as rapid rotators, spun up by binary mass transfer, or spun up during the main-sequence evolution of B stars. From a photometric search for Be stars in 55 open clusters and followup spectra of 11 clusters, we found that ~75% of our Be stars show evidence of having been spun up by binary mass transfer, while the other scenarios do not produce significant numbers of Be stars. However, this result does not include 86 Be star candidates in the remaining clusters whose emission status must be confirmed spectroscopically. In addition, over three years of observations of 11 clusters, we have identified 8 Be stars that have undergone disk outbursts and 7 whose disks have disappeared. The rate of variability does not seem to be constant, and we will investigate stellar and cluster properties that may affect their long term variability. New spectra of 20 open clusters will provide confirmation of most of our remaining Be star candidates as well as a 4- year time baseline to study disk appearances and disappearances in these clusters.
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