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Session 82 - Spirals & Irregulars.
Display session, Friday, January 09
Exhibit Hall,
The post-main sequence evolution of massive stars is a crucial, but still poorly understood phase. In this regime, Luminous Blue Variables play an important role as the descendants of massive main sequence O stars, and the probable progenitors of Wolf-Rayet stars. Unfortunately, the LBV lifetime and their progenitors are not well constrained observationally, because of the low number of LBVs identified in various nearby galaxies. We are addressing this problem in two ways. We have developed an effective search technique to identify LBV candidates in nearby galaxies, to increase the sample of massive stars with extreme mass loss rates. We are also studying the environments of known LBVs and new candidates to obtain constraints on their evolutionary status.
We have identifed 7 new candidate LBVs in the NE half of M31 with optical spectroscopy from the ARC 3.5-m telescope. We have obtained high resolution U, B, R, and H\alpha images of the candidates and their environments with the WIYN 3.5-m telescope. We limit the ages of the candidate LBVs by studying the nearby HII regions and OB associations. The color-magnitude diagrams show evidence for age variations among potential parent associations. In addition, most of our LBV candidates are no longer associated with prominent HII regions, indicating ages of at least several million years. This is in agreement with a post-main sequence evolutionary stage. We also present ARC 3.5-m J,H, and K photometry of the candidates. These data allow us to search for IR excess emission, which may help to further classify the candidate LBVs.
