Boron Abundances Across the 'Li-Be Dip' in the Hyades
| Autor: | Boesgaard, Ann Merchant, Deliyannis, Michael G. Lum. Constantine P., King, Jeremy R., Pinsonneault, Marc H., Somers, Garrett |
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| Rok vydání: | 2016 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/0004-637X/830/1/49 |
| Popis: | Dramatic deficiencies of Li in the mid-F dwarf stars of the Hyades cluster were discovered by Boesgaard & Tripicco. Boesgaard & King discovered corresponding, but smaller, deficiencies in Be in the same narrow temperature region in the Hyades. With the Space Telescope Imaging Spectrograph on the Hubble Space Telescope we investigate B abundances in the Hyades F stars to look for a potential B dip using the B I resonance line at 2496.8 A. The light elements, Li, Be, and B, are destroyed inside stars at increasingly hotter temperatures: 2.5, 3.5, and 5x10^6 K respectively. Consequently, these elements survive to increasingly greater depths in a star and their surface abundances indicate the depth and thoroughness of mixing in the star. We have (re)determined Li abundances/upper limits for 79 Hyades dwarfs, Be for 43 stars, and B in five stars. We find evidence for a small drop in the B abundance across the Li-Be dip. The B abundances for the four stars in the temperature range 6100-6730 K fit the B-Be correlation found previously by Boesgaard et al. Models of rotational mixing produce good agreement with the relative depletions of Be and B in the dip region. We have compared our nLTE B abundances for the three high B stars on either side of the Li-Be dip with those found by Duncan et al. for the two Hyades giants. This confirms the factor of ~10 decline in the B abundance in the Hyades giants as predicted by dilution due to the deepening of the surface convection zone. Comment: Accepted by Ap. J. 18 pages text + 5 tables + 15 figures = 43 pages |
| Databáze: | arXiv |
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