TY - JOUR

T1 - Search for Sodium-rich Stars among Metal-poor Stars

AU - Pereira, C.B.

AU - Holanda, N.

AU - Drake, N. A.

AU - Roig, F.

PY - 2019/2/10

Y1 - 2019/2/10

N2 - Sodium-rich stars are often found in globular clusters giants. However, some sodium-rich stars have been found among field metal-poor stars. These stars are considered as evaporated from globular clusters. Identified such kind of stars among the field stars in the Galaxy may provide insights of which mechanism was responsible for the ejection from a globular cluster and may reveal some chemical peculiarity. Therefore, we started a search, using high-resolution spectroscopy, among metal-poor stars from several sources of the literature to find a sodium-rich star. Here we present the results for the temperature, gravity, metallicity, and sodium abundances for the stars of our sample. For many of them we determined the temperature, gravity, metallicity, and sodium abundances for the first time. As a result of our search we found one star, CD-23°16310, which has a [Na/Fe] ratio of +1.09. We also show that CD-23°16310 is not a carbon-enhanced metal-poor (CEMP) star since carbon is not enriched but is nitrogen-rich. We did not detect any variation of the radial velocity that would support the hypothesis of mass transfer. Thus, the high sodium and nitrogen abundance could be due to a strong internal mixing process, suggesting that CD-23°16310 is an early asymptotic giant branch star.

AB - Sodium-rich stars are often found in globular clusters giants. However, some sodium-rich stars have been found among field metal-poor stars. These stars are considered as evaporated from globular clusters. Identified such kind of stars among the field stars in the Galaxy may provide insights of which mechanism was responsible for the ejection from a globular cluster and may reveal some chemical peculiarity. Therefore, we started a search, using high-resolution spectroscopy, among metal-poor stars from several sources of the literature to find a sodium-rich star. Here we present the results for the temperature, gravity, metallicity, and sodium abundances for the stars of our sample. For many of them we determined the temperature, gravity, metallicity, and sodium abundances for the first time. As a result of our search we found one star, CD-23°16310, which has a [Na/Fe] ratio of +1.09. We also show that CD-23°16310 is not a carbon-enhanced metal-poor (CEMP) star since carbon is not enriched but is nitrogen-rich. We did not detect any variation of the radial velocity that would support the hypothesis of mass transfer. Thus, the high sodium and nitrogen abundance could be due to a strong internal mixing process, suggesting that CD-23°16310 is an early asymptotic giant branch star.

KW - химическое содержание звезд

KW - звезды AGB и post-AGB

KW - химически-пекулярные звезды

KW - эволюция звезд

KW - фундаментальные параметры звезд

KW - stars: AGB and post-AGB

KW - stars: abundances

KW - stars: chemically peculiar

KW - stars: evolution

KW - stars: fundamental parameters

KW - ABUNDANCE PATTERNS

KW - ELEMENTS

KW - EVOLUTION

KW - GALACTIC DISK

KW - GIANT BRANCH

KW - HALO

KW - KINEMATICS

UR - http://adsabs.harvard.edu/abs/2019AJ....157...70P

UR - http://www.scopus.com/inward/record.url?scp=85062915522&partnerID=8YFLogxK

UR - http://www.mendeley.com/research/search-sodiumrich-stars-among-metalpoor-stars

U2 - 10.3847/1538-3881/aaf71e

DO - 10.3847/1538-3881/aaf71e

M3 - Article

VL - 157

JO - Astronomical Journal

JF - Astronomical Journal

SN - 0004-6256

IS - 2

M1 - 70

ER -