2012A&A...547A..76P


Query : 2012A&A...547A..76P

2012A&A...547A..76P - Astronomy and Astrophysics, volume 547A, 76-76 (2012/11-1)

The occurrence of nitrogen-enhanced metal-poor stars: implications for the initial mass function in the early Galactic halo.

POLS O.R., IZZARD R.G., STANCLIFFE R.J. and GLEBBEEK E.

Abstract (from CDS):

Most carbon-enhanced metal-poor (CEMP) stars are thought to result from past mass transfer of He-burning material from an asymptotic giant branch (AGB) star to a low-mass companion star, which we now observe as a CEMP star. Because AGB stars of intermediate mass efficiently cycle carbon into nitrogen in their envelopes, the same evolution scenario predicts the existence of a population of nitrogen-enhanced metal-poor (NEMP) stars, with [N/Fe]>1 and [N/C]>0.5. Such NEMP stars are rare, although their occurrence depends on metallicity: they appear to be more common at [Fe/H]←2.8 by about a factor of 10 compared to less metal-poor stars. We analyse the observed sample of metal-poor stars with measurements of both carbon and nitrogen to derive firm constraints on the occurrence of NEMP stars as a function of metallicity. We compare these constraints to binary population synthesis calculations in which we vary the initial distributions of mass, mass ratio and binary orbital periods. We show that the observed paucity of NEMP stars at [Fe/H]>-2.8 does not allow for large modifications in the initial mass function, as have been suggested in the literature to account for the high frequency of CEMP stars. The situation at lower metallicity is less clear, and we do not currently have stellar models to perform this comparison for [Fe/H]←2.8. However, unless intermediate-mass AGB stars behave very differently at such low metallicity, the observed NEMP frequency at [Fe/H]←2.8 appears incompatible with the top-heavy forms of the initial mass function suggested in the literature.

Abstract Copyright:

Journal keyword(s): stars: carbon - binaries: close - stars: chemically peculiar - Galaxy: halo - Galaxy: stellar content - reactions nuclear, nucleosynthesis, abundances

Simbad objects: 19

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Number of rows : 19
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 PHL 8278 Pe* 02 28 26.5490110152 -21 33 00.976151736   14.862 14.510 14.292 14.015 CEMP-s 19 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 26 0
3 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 6487 1
4 HE 0400-2030 Pe* 04 02 14.8021418088 -20 21 53.533679904   14.921 14.033 13.605 13.164 CEMP-s 18 0
5 HD 25329 PM* 04 03 14.9979736362 +35 16 23.805785323 9.75 9.37 8.50 7.75 7.23 K1VbFe-2 355 0
6 HE 1031-0020 Pe* 10 34 24.2082300456 -00 36 08.378366148     14.30     CEMP-s 23 0
7 * eta Car Em* 10 45 03.5377808928 -59 41 04.051599720 6.37 7.03 6.48 4.90 4.41 OBepec 2350 0
8 Wolf 1492 Pe* 13 40 02.4921849768 -00 02 18.750053436 11.601 11.832 11.451 11.184 10.892 sdF0: 273 0
9 HE 1410+0213 Pe* 14 13 06.5623389120 +01 59 21.911258400   14.29 13.25 12.734 12.297 CEMP-no 22 0
10 HE 1413-1954 Pe* 14 16 04.7119539312 -20 08 54.089976552     15.235   14.593 CEMP-no 15 0
11 NAME Upper Sco-Cen As* 16 15 -24.2           ~ 1258 1
12 ATO J256.8913+58.8499 RR* 17 07 33.9318852312 +58 50 59.711493732   16.209 15.635 15.977   F5kA2Bapec 25 0
13 BPS CS 30314-0067 Pe* 20 52 50.9878832880 -34 19 40.547263404   12.98 11.85 11.175 10.583 CEMP-no 29 0
14 UCAC4 219-185099 Pe* 21 30 32.1818994960 -46 16 24.614480388   13.447 12.167 11.902 10.908 ~ 54 0
15 HD 206983 Pe* 21 46 09.3423868872 -15 14 39.766213896   11.1 9.45     GpBa 42 1
16 HE 2150-0825 Pe* 21 53 00.1626443880 -08 11 18.214399320     14.959   14.316 ~ 14 0
17 BPS CS 22960-0053 Pe* 22 16 17.0867216280 -43 54 19.738138428 15.69 15.705 14.950 14.537 14.046 CEMP-s 24 0
18 2MASS J22564259-4201506 * 22 56 42.5958306240 -42 01 50.713838940   14.447 13.483 12.982 12.465 ~ 2 0
19 HE 2323-0256 Pe* 23 26 29.8073738880 -02 39 58.036383180   15.12 14.36   13.358 CEMP-no 175 0

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2022.11.28-08:11:52

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