2019/10/16 by Ann Merchant Boesgaard, Boesgaard, Ann Merchant, Michael G. Lum +3 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #FOS: Physical sciences #Scientific Research and Discoveries #Solar and Stellar Astrophysics (astro-ph.SR) #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.1910.07656
openalex publication_date 2019/10/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The surface content of lithium (Li) and beryllium (Be) provide insights into\nthe mixing and circulation mechanisms in stellar interiors. The old open\ncluster, M 67, has been well-studied for Li abundances in both main-sequence\nand evolved stars. The Be abundances give us a probe to a deeper level in\nstars. We have taken high-resolution spectra with Keck I with HIRES to\ndetermine Be abundances along the subgiant branch of M 67, where there are\ndramatic depletions of Li. These subgiants range in mass from 1.26 to 1.32\nM odot and have evolved from main-sequence stars that would have occupied\nthe region of the Li-Be dip found in younger clusters. Lithium abundances have\nbeen adjusted to the same scale for 103 stars in M 67 by Pace et al. The more\nmassive stars - now the coolest and furthest-evolved from the main-sequence\n- show a drop in Li by a factor of 400 across the subgiant branch. Our new Be\nabundances also show a decline, but by a factor of \∼50. The two elements\ndecline together with Li showing a steeper decline in these subgiants than it\ndoes in the Li-Be dip stars. The relative decline in Be abundance compared to\nLi is remarkably well fit by the models of Sills & Deliyannis, made\nspecifically for the subgiants in M 67. Those models include the effects of\nmixing induced by stellar rotation. These M 67 subgiants show the effects of\nboth main-sequence depletion and post-main-sequence dilution of both Li and Be.\n