Query : 2021A&A...645A..10G

2021A&A...645A..10G - Astronomy and Astrophysics, volume 645A, 10-10 (2021/1-1)

Nucleosynthetic yields of Z = 10–5 intermediate-mass stars.


Abstract (from CDS):

Context. Observed abundances of extremely metal-poor stars in the Galactic halo hold clues for understanding the ancient universe. Interpreting these clues requires theoretical stellar models in a wide range of masses in the low-metallicity regime. The existing literature is relatively rich with extremely metal-poor massive and low-mass stellar models. However, relatively little information is available on the evolution of intermediate-mass stars of Z≤10–5, and the impact of the uncertain input physics on the evolution and nucleosynthesis has not yet been systematically analysed.
Aims. We aim to provide the nucleosynthetic yields of intermediate-mass Z=10–5 stars between 3 and 7.5M, and quantify the effects of the uncertain wind rates. We expect these yields could eventually be used to assess the contribution to the chemical inventory of the early universe, and to help interpret abundances of selected C-enhanced extremely metal-poor (CEMP) stars.
Methods. We compute and analyse the evolution of surface abundances and nucleosynthetic yields of Z=10–5 intermediate-mass stars from their main sequence up to the late stages of their thermally pulsing (Super) AGB phase, with different prescriptions for stellar winds. We use the postprocessing codeMONSOON to compute the nucleosynthesis based on the evolution structure obtained with the Monash-Mount Stromlo stellar evolution codeMONSTAR. By comparing our models and others from the literature, we explore evolutionary and nucleosynthetic trends with wind prescriptions and with initial metallicity (in the very low-Z regime). We also compare our nucleosynthetic yields to observations of CEMP-s stars belonging to the Galactic halo.
Results. The yields of intermediate-mass extremely metal-poor stars reflect the effects of very deep or corrosive second dredge-up (for the most massive models), superimposed with the combined signatures of hot-bottom burning and third dredge-up. Specifically, we confirm the reported trend that models with initial metallicity Zini≤10–3 give positive yields of 12C, 15N, 16O, and 26Mg. The 20Ne, 21Ne, and 24Mg yields, which were reported to be negative at Zini≥10–4, become positive for Z=10–5. The results using two different prescriptions for mass-loss rates differ widely in terms of the duration of the thermally pulsing (Super) AGB phase, overall efficiency of the third dredge-up episode, and nucleosynthetic yields. We find that the most efficient of the standard wind rates frequently used in the literature seems to favour agreement between our yield results and observational data. Regardless of the wind prescription, all our models become N-enhanced EMP stars.

Abstract Copyright: © ESO 2020

Journal keyword(s): stars: abundances - stars: AGB and post-AGB - stars: evolution - stars: Population II

VizieR on-line data: <Available at CDS (J/A+A/645/A10): z1em5bl.dat z1em5vw.dat>

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 NGC 362 GlC 01 03 14.26 -70 50 55.6     6.58     ~ 1089 0
2 BPS CS 29528-0041 Pe* 02 29 25.2514644552 -18 13 28.025186448 14.83 15.20 14.59 14.67   CEMP-no 27 0
3 HE 0450-4902 Pe* 04 51 43.2538838712 -48 57 25.202919240   16.23 15.84 15.90   CEMP-s 7 0
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 17478 0
5 HE 1029-0546 Pe* 10 31 48.1191917592 -06 01 43.943123568   15.987 15.632 15.316   CEMP-s 9 0
6 2MASS J11140709+1828320 Pe* 11 14 07.0924277328 +18 28 31.823630328           CEMP-s 8 0
7 SDSS J114323.42+202058.0 Pe* 11 43 23.4373926864 +20 20 58.123889232           CEMP-s 9 0
8 NAME SDSS J1349-0229 Pe* 13 49 13.5415394784 -02 29 42.784646424           CEMP-s 24 0
9 UCAC4 378-069857 Pe* 14 42 09.39690 -14 32 56.0022     15.46     CEMP-s 5 0
10 M 12 GlC 16 47 14.18 -01 56 54.7     6.07     ~ 681 0

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