2015A&A...583A..87S


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST04:38:27

2015A&A...583A..87S - Astronomy and Astrophysics, volume 583A, 87-87 (2015/11-1)

Post first dredge-up [C/N] ratio as age indicator. Theoretical calibration.

SALARIS M., PIETRINFERNI A., PIERSIMONI A.M. and CASSISI S.

Abstract (from CDS):

We performed a detailed analysis of the use of [C/N] measured in red giant branch stars between the completion of the first dredge up and the red giant branch bump ([C/N]FDU) as age indicator. [C/N]FDU cannot give accurate ages for individual stars, but may provide a general chronology for the formation of composite populations and add constraints to analyses of red giants from surface gravity-effective temperature diagrams. We provide a theoretical calibration of [C/N]FDU in terms of total metallicity [M/H] and age, for ages greater than ∼1Gyr, which we tested against variations in the initial heavy element distribution (scaled-solar vs. α-enhanced), efficiency of overshooting from MS convective cores and from the convective envelopes, variations in the initial He abundance and in the mixing length parameter. Our calibration is compared with a small sample of available measurements of [C/N]FDU in star clusters and halo field stars, which at least qualitatively confirm the overall trend of the predicted [C/N]FDU with age and [M/H]. The use of [C/N]FDU-[M/H]-age relations obtained from independent sets of stellar evolution calculations cause age differences (for a given [C/N]FDU and [M/H] pair) up to ∼2Gyr. More accurate spectroscopic measurements of [C/N]FDU in star clusters with well-established ages and metallicities are required to better test theoretical calibrations of this age indicator.

Abstract Copyright:

Journal keyword(s): convection - galaxies: formation - stars: abundances - stars: evolution - stars: interiors

Simbad objects: 5

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Number of rows : 5

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 752 OpC 01 57 41 +37 47.1           ~ 537 0
2 NGC 2506 OpC 08 00 01 -10 46.2   8.28 7.6     ~ 221 0
3 NGC 2682 OpC 08 51 18 +11 48.0           ~ 2032 0
4 NGC 6791 OpC 19 20 53 +37 46.3   10.52 9.5     ~ 869 0
5 NGC 6819 OpC 19 41 18 +40 11.2   8.21 7.3     ~ 465 0

    Equat.    Gal    SGal    Ecl

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2020.07.08-04:38:27

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