Hungry Red Supergiants: Investigating Stellar Mergers in Evolved Massive Stars
Abstract
The percentage of massive main-sequence OB stars in binary systems is high, some arguing that it may be as large as 80-100%. However the binary fraction of red supergiants (RSGs) ranges from 15-40%, despite these stars being the evolved descendants of OB stars. One possible explanation for the lack of observed binary RSGs is that many of them have merged. As a binary OB system evolves, the more massive star will leave the main sequence first and evolve into a RSG. If the two stars are close enough, the RSG will expand enough to engulf the secondary, causing a merger as they spin together and gain angular momentum. This event will increase the rotational velocity of the RSG by a measurable amount (> 5 km/s) and lead to unique abundances and physical properties. We've recently observed ~80 Galactic RSGs with EXPRES, a high-resolution spectrograph on the Lowell Discovery Telescope, and are in the process of using this dataset to determine the relative importance of RSG mergers before these stars end their lives as supernovae.
This work was partially supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51516 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- January 2023
- Bibcode:
- 2023AAS...24140101N