2006A&A...447..623M


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.04CET20:09:23

2006A&A...447..623M - Astronomy and Astrophysics, volume 447, 623-639 (2006/2-4)

The early star generations: the dominant effect of rotation on the CNO yields.

MEYNET G., EKSTROEM S. and MAEDER A.

Abstract (from CDS):

We examine the role of rotation on the evolution and chemical yields of very metal-poor stars. The models include the same physics, which was applied successfully at the solar Z and for the SMC, in particular, shear diffusion, meridional circulation, horizontal turbulence, and rotationally enhanced mass loss. Models of very low Z experience a much stronger internal mixing in all phases than at solar Z. Also, rotating models at very low Z, contrary to the usual considerations, show a large mass loss, which mainly results from the efficient mixing of the products of the 3α reaction into the H-burning shell. This mixing allows convective dredge-up to enrich the stellar surface in heavy elements during the red supergiant phase, which in turn favours a large loss of mass by stellar winds, especially as rotation also increases the duration of this phase. On the whole, the low Z stars may lose about half of their mass. Massive stars initially rotating at half of their critical velocity are likely to avoid the pair-instability supernova. The chemical composition of the rotationally enhanced winds of very low Z stars show large CNO enhancements by factors of 103 to 107, together with large excesses of 13C and 17O and moderate amounts of Na and Al. The excesses of primary N are particularly striking. When these ejecta from the rotationally enhanced winds are diluted with the supernova ejecta from the corresponding CO cores, we find [C/Fe], [N/Fe], [O/Fe] abundance ratios that are very similar to those observed in the C-rich, extremely metal-poor stars (CEMP). We show that rotating AGB stars and rotating massive stars have about the same effects on the CNO enhancements. Abundances of s-process elements and the 12C/13C ratio could help us to distinguish between contributions from AGB and massive stars.

Abstract Copyright:

Journal keyword(s): stars: evolution - stars: rotation - stars: abundances - stars: mass loss - nuclear reactions, nucleosynthesis, abundances

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9708 1
2 HE 0107-5240 Pe* 01 09 29.1554552993 -52 24 34.203535506   15.89 15.07 15.10 14.283 CEMP-no 231 0
3 G 77-61 Pe* 03 32 38.0871477505 +01 58 00.010460312   15.60 13.90 12.9   dC-J_CH5 126 0
4 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15211 1
5 HE 1327-2326 Pe* 13 30 05.9395582011 -23 41 49.699027289 13.761 14.01 13.55 13.50 12.803 CEMP-no 220 0
6 BPS CS 29498-0043 Pe* 21 03 52.1197489072 -29 42 50.344264361   14.8 13.72 13.013 12.406 CEMP-no 88 0
7 HE 2323-0256 Pe* 23 26 29.8073543039 -02 39 58.037206596   15.12 14.36   13.358 CEMP-no 172 0

    Equat.    Gal    SGal    Ecl

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