2016A&A...587A..50A


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.14CEST22:29:31

2016A&A...587A..50A - Astronomy and Astrophysics, volume 587A, 50-50 (2016/3-1)

How plausible are the proposed formation scenarios of CEMP-r/s stars?

ABATE C., STANCLIFFE R.J. and LIU Z.-W.

Abstract (from CDS):

CEMP-r/s stars are metal-poor stars with enhanced abundances of carbon and heavy elements associated with the slow and rapid neutron-capture process (s- and r-elements, respectively). It is believed that carbon and s-elements were accreted in the past from the wind of a primary star in the asymptotic giant branch (AGB) phase of evolution, a scenario that is generally accepted to explain the formation of CEMP stars that are only enhanced in s-elements (CEMP-s stars). The origin of r-element-enrichment in CEMP-r/s stars is currently debated and many formation scenarios have been put forward. We aim to determine the likelihood of the scenarios proposed to explain the formation of CEMP-r/s stars. We calculate the frequency of CEMP-r/s stars among CEMP-s stars for a variety of formation scenarios, and we compare it with that determined from an observed sample of CEMP-r/s stars collected from the literature. The theoretical frequency of CEMP-r/s stars predicted in most formation scenarios underestimates the observed ratio by at least a factor of five. If the enrichments in s- and r-elements are independent, the model ratio of CEMP-r/s to CEMP-s stars is about 22%, that is approximately consistent with the lowest estimate of the observed ratio. However, this model predicts that about one third of all carbon-normal stars have [Ba/Fe] and [Eu/Fe] higher than one, and that 40% of all CEMP stars have [Ba/Eu]≤0. Stars with these properties are at least ten times rarer in our observed sample. The intermediate or i-process, which is supposedly active in some circumstances during the AGB phase, could provide an explanation of the origin of CEMP-r/s stars, similar to that of CEMP-s stars, in the context of wind mass accretion in binary systems. Further calculations of the nucleosynthesis of the i-process and of the detailed evolution of late AGB stars are needed to investigate if this scenario predicts a CEMP-r/s star frequency consistent with the observations.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: AGB and post-AGB - stars: Population II - stars: chemically peculiar - Galaxy: halo - binaries: general

Simbad objects: 6

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Number of rows : 6

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 BPS CS 29497-0004 Pe* 00 28 06.9155330651 -26 03 04.268822971   14.76 14.07 13.583 13.116 ~ 42 0
2 BPS CS 31082-0001 Pe* 01 29 31.1311330115 -16 00 45.496485322 12.527 12.427 11.642 11.189 10.713 CEMP 243 0
3 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5669 1
4 BD-01 2582 Pe* 11 53 37.3233658419 -02 00 36.726031369   10.29 9.60     CEMP-s 95 0
5 V* V4334 Sgr NL* 17 52 32.69 -17 41 08.0   12.01       F2Ia 329 0
6 Wolf 984 PM* 22 05 01.4079846222 +08 38 18.901348262   12.61   11.2   sdF8: 40 0

    Equat.    Gal    SGal    Ecl

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2020.07.14-22:29:31

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