The puzzling Li-rich red giant associated with NGC 6819

Joleen K. Carlberg, Verne V. Smith, Katia Cunha, Steven R. Majewski, Szabolcs Mészáros, Matthew Shetrone, Carlos Allende Prieto, Dmitry Bizyaev, Keivan G. Stassun, Scott W. Fleming, Gail Zasowski, Fred Hearty, David L. Nidever, Donald P. Schneider, Jon A. Holtzman, Peter M. Frinchaboy

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

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 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.

Original languageEnglish (US)
Article number7
JournalAstrophysical Journal
Volume802
Issue number1
DOIs
StatePublished - Mar 20 2015

Fingerprint

stars
observatory
dredger
galactic evolution
dilution
experiment
diagram
observatories
gravity
stellar interiors
red giant stars
asteroseismology
ascent
color-magnitude diagram
radial velocity
set theory
luminosity
chemistry
gravitation
augmentation

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Carlberg, J. K., Smith, V. V., Cunha, K., Majewski, S. R., Mészáros, S., Shetrone, M., ... Frinchaboy, P. M. (2015). The puzzling Li-rich red giant associated with NGC 6819. Astrophysical Journal, 802(1), [7]. https://doi.org/10.1088/0004-637X/802/1/7
Carlberg, Joleen K. ; Smith, Verne V. ; Cunha, Katia ; Majewski, Steven R. ; Mészáros, Szabolcs ; Shetrone, Matthew ; Prieto, Carlos Allende ; Bizyaev, Dmitry ; Stassun, Keivan G. ; Fleming, Scott W. ; Zasowski, Gail ; Hearty, Fred ; Nidever, David L. ; Schneider, Donald P. ; Holtzman, Jon A. ; Frinchaboy, Peter M. / The puzzling Li-rich red giant associated with NGC 6819. In: Astrophysical Journal. 2015 ; Vol. 802, No. 1.
@article{c6a5f996dddc4963b274313e951af4fc,
title = "The puzzling Li-rich red giant associated with NGC 6819",
abstract = "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 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.",
author = "Carlberg, {Joleen K.} and Smith, {Verne V.} and Katia Cunha and Majewski, {Steven R.} and Szabolcs M{\'e}sz{\'a}ros and Matthew Shetrone and Prieto, {Carlos Allende} and Dmitry Bizyaev and Stassun, {Keivan G.} and Fleming, {Scott W.} and Gail Zasowski and Fred Hearty and Nidever, {David L.} and Schneider, {Donald P.} and Holtzman, {Jon A.} and Frinchaboy, {Peter M.}",
year = "2015",
month = "3",
day = "20",
doi = "10.1088/0004-637X/802/1/7",
language = "English (US)",
volume = "802",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",

}

Carlberg, JK, Smith, VV, Cunha, K, Majewski, SR, Mészáros, S, Shetrone, M, Prieto, CA, Bizyaev, D, Stassun, KG, Fleming, SW, Zasowski, G, Hearty, F, Nidever, DL, Schneider, DP, Holtzman, JA & Frinchaboy, PM 2015, 'The puzzling Li-rich red giant associated with NGC 6819', Astrophysical Journal, vol. 802, no. 1, 7. https://doi.org/10.1088/0004-637X/802/1/7

The puzzling Li-rich red giant associated with NGC 6819. / Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Majewski, Steven R.; Mészáros, Szabolcs; Shetrone, Matthew; Prieto, Carlos Allende; Bizyaev, Dmitry; Stassun, Keivan G.; Fleming, Scott W.; Zasowski, Gail; Hearty, Fred; Nidever, David L.; Schneider, Donald P.; Holtzman, Jon A.; Frinchaboy, Peter M.

In: Astrophysical Journal, Vol. 802, No. 1, 7, 20.03.2015.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The puzzling Li-rich red giant associated with NGC 6819

AU - Carlberg, Joleen K.

AU - Smith, Verne V.

AU - Cunha, Katia

AU - Majewski, Steven R.

AU - Mészáros, Szabolcs

AU - Shetrone, Matthew

AU - Prieto, Carlos Allende

AU - Bizyaev, Dmitry

AU - Stassun, Keivan G.

AU - Fleming, Scott W.

AU - Zasowski, Gail

AU - Hearty, Fred

AU - Nidever, David L.

AU - Schneider, Donald P.

AU - Holtzman, Jon A.

AU - Frinchaboy, Peter M.

PY - 2015/3/20

Y1 - 2015/3/20

N2 - 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 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.

AB - 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 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.

UR - http://www.scopus.com/inward/record.url?scp=84925759973&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84925759973&partnerID=8YFLogxK

U2 - 10.1088/0004-637X/802/1/7

DO - 10.1088/0004-637X/802/1/7

M3 - Article

AN - SCOPUS:84925759973

VL - 802

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 7

ER -

Carlberg JK, Smith VV, Cunha K, Majewski SR, Mészáros S, Shetrone M et al. The puzzling Li-rich red giant associated with NGC 6819. Astrophysical Journal. 2015 Mar 20;802(1). 7. https://doi.org/10.1088/0004-637X/802/1/7