Bibcode
Carlberg, J. K.; Smith, Verne V.; Cunha, Katia; Majewski, Steven R.; Mészáros, Szabolcs; Shetrone, Matthew; Allende Prieto, C.; Bizyaev, Dmitry; Stassun, Keivan G.; Fleming, Scott W.; Zasowski, Gail; Hearty, Fred; Nidever, David L.; Schneider, Donald P.; Holtzman, Jon A.; Frinchaboy, Peter M.
Bibliographical reference
The Astrophysical Journal, Volume 802, Issue 1, article id. 7, 11 pp. (2015).
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3
2015
Journal
Citations
31
Refereed citations
29
Description
A Li-rich red giant (RG) star (2M19411367+4003382) recently discovered
in the direction of NGC 6819 belongs to the rare subset of Li-rich stars
that have not yet evolved to the luminosity bump, an evolutionary stage
where models predict Li can be replenished. The currently favored model
to explain Li enhancement in first-ascent RGs like 2M19411367+4003382
requires deep mixing into the stellar interior. Testing this model
requires a measurement of 12C/13C, which is
possible to obtain from Apache Point Observatory Galactic Evolution
Experiment (APOGEE) spectra. However, the Li-rich star also has abnormal
asteroseismic properties that call into question its membership in the
cluster, even though its radial velocity and location on
color–magnitude diagrams are consistent with membership. To
address these puzzles, we have measured a wide array of abundances in
the Li-rich star and three comparison stars using spectra taken as part
of the APOGEE survey to determine the degree of stellar mixing, address
the question of membership, and measure the surface gravity. We confirm
that the Li-rich star is a RG with the same overall chemistry as the
other cluster giants. However, its log g is significantly lower,
consistent with the asteroseismology results and suggestive of a very
low mass if the star is indeed a cluster member. Regardless of the
cluster membership, the 12C/13C and C/N ratios of
the Li-rich star are consistent with standard first dredge-up,
indicating that Li dilution has already occurred, and inconsistent with
internal Li enrichment scenarios that require deep mixing.
Related projects
Chemical Abundances in Stars
Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to
Carlos
Allende Prieto