Boron Abundances in Early B Dwarfs of the Galactic Open Cluster NGC 3293

New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron me...

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Bibliographic Details
Published in:The Astrophysical journal 2024-06, Vol.968 (1), p.1
Main Authors: Proffitt, Charles R., Jin, Harim, Daflon, Simone, Lennon, Daniel J., Langer, Norbert, Cunha, Katia, Monroe, Talawanda
Format: Article
Language:English
Subjects:
Abundance
B stars
Boron
Depletion
Galactic clusters
Hubble Space Telescope
Luminosity
Main sequence stars
Space telescopes
Stars
Stellar abundances
Stellar evolution
Stellar physics
Stellar populations
Stellar rotation
Ultraviolet spectra
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Summary:New boron abundances or upper limits have been determined for eight early B stars in the young Galactic open cluster NGC 3293, using UV spectra obtained by the Hubble Space Telescope Cosmic Origins Spectrograph. With previous observations, there are now 18 early B stars in this cluster with boron measurements. Six of the newly observed stars have projected rotational velocities greater than 200 km s −1 , allowing new constraints on rotationally driven mixing in main-sequence stars. When comparing to synthetic model populations, we find that the majority of our sample stars agree well with the predicted trends of stronger boron depletion for larger rotation and for larger mass or luminosity. Based on those, a smaller than the canonical rotational mixing efficiency ( f c ≈ 0.0165 versus the more standard value of 0.033) appears to be favored. In addition, the five mostly slowly rotating stars, when considered as a group, tend to show more boron depletion than expected from rotational mixing, and we speculate that most or all of these originate from binary mergers.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad3e62