Astrophys. J., 830, 49-49 (2016/October-2)
Boron abundances across the "Li-Be dip" in the Hyades cluster.
BOESGAARD A.M., LUM M.G., DELIYANNIS C.P., KING J.R., PINSONNEAULT M.H. and SOMERS G.
Abstract (from CDS):
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. Using 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 5 x 106 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 for 5 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.
© 2016. The American Astronomical Society. All rights reserved.
open clusters and associations: general - open clusters and associations: individual: Hyades - stars: abundances - stars: evolution - stars: late-type - stars: solar-type - stars: solar-type
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