2016A&A...586A.160H


Query : 2016A&A...586A.160H

2016A&A...586A.160H - Astronomy and Astrophysics, volume 586A, 160-160 (2016/2-1)

The role of binaries in the enrichment of the early Galactic halo. II. Carbon-enhanced metal-poor stars: CEMP-no stars.

HANSEN T.T., ANDERSEN J., NORDSTROEM B., BEERS T.C., PLACCO V.M., YOON J. and BUCHHAVE L.A.

Abstract (from CDS):

The detailed composition of most metal-poor halo stars has been found to be very uniform. However, a fraction of 20-70% (increasing with decreasing metallicity) exhibit dramatic enhancements in their abundances of carbon; these are the so-called carbon-enhanced metal-poor (CEMP) stars. A key question for Galactic chemical evolution models is whether this non-standard composition reflects that of the stellar natal clouds or is due to local, post-birth mass transfer of chemically processed material from a binary companion; CEMP stars should then all be members of binary systems. Our aim is to determine the frequency and orbital parameters of binaries among CEMP stars with and without over-abundances of neutron-capture elements - CEMP-s and CEMP-no stars, respectively - as a test of this local mass-transfer scenario. This paper discusses a sample of 24 CEMP-no stars, while a subsequent paper will consider a similar sample of CEMP-s stars. High-resolution, low S/N spectra of the stars were obtained at roughly monthly intervals over a time span of up to eight years with the FIES spectrograph at the Nordic Optical Telescope. Radial velocities of ∼100m/s precision were determined by cross-correlation after each observing night, allowing immediate, systematic follow-up of any variable object. Most programme stars exhibit no statistically significant radial-velocity variation over this period and appear to be single, while four are found to be binaries with orbital periods of 300-2000 days and normal eccentricity; the binary frequency for the sample is 17±9%. The single stars mostly belong to the recently identified low-C band, while the binaries have higher absolute carbon abundances. We conclude that the nucleosynthetic process responsible for the strong carbon excess in these ancient stars is unrelated to their binary status; the carbon was imprinted on their natal molecular clouds in the early Galactic interstellar medium (ISM) by an even earlier external source, strongly indicating that the CEMP-no stars are likely bona fide second-generation stars. We discuss potential production sites for carbon and its transfer across interstellar distances in the early ISM, and the implications for the composition of high-redshift DLA systems.

Abstract Copyright:

Journal keyword(s): Galaxy: formation - Galaxy: halo - stars: chemically peculiar - binaries: spectroscopic - ISM: structure

Errata: eratum vol. 620, art. C3 (2018)

Simbad objects: 36

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Number of rows : 36
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 HE 0017+0055 Pe* 00 20 21.6000581352 +01 12 06.817571136   12.991 11.66 10.773 10.186 CEMP-rs 24 0
2 BPS CS 30324-0063 Pe* 00 22 44.8620794952 -17 24 29.140962984   13.824 12.887     CEMP-no 19 0
3 BPS CS 29527-0015 Pe* 00 29 10.6814565504 -19 10 07.305102624   14.61 14.24     CEMP-no 53 0
4 BPS CS 22166-0016 Pe* 00 58 23.8415767344 -14 47 06.878622912   13.34 12.75 12.324 11.898 CEMP-no 21 0
5 HE 0107-5240 Pe* 01 09 29.1555567432 -52 24 34.202039148   15.89 15.07 15.10 14.283 CEMP-no 236 0
6 BPS CS 31082-0001 RG* 01 29 31.1311443552 -16 00 45.495314460 12.527 12.427 11.642 11.189 10.713 CEMP 277 0
7 HE 0219-1739 Pe* 02 21 41.2958950176 -17 25 37.031081124   15.85 14.10 14.035 13.444 CEMP-no 9 0
8 BD+44 493 Pe* 02 26 49.7390353632 +44 57 46.523771136   9.63 9.11     CEMP-no 96 0
9 HE 0233-0343 Pe* 02 36 29.7931635456 -03 30 06.029112888   15.867 15.430 15.171 14.818 CEMP-no 30 0
10 UCAC4 115-002803 Pe* 03 13 00.3747928560 -67 08 39.336144504   15.442 14.753 14.639   CEMP-no 100 0
11 HE 0405-0526 Pe* 04 07 46.99800 -05 18 10.9863           CEMP-no 4 0
12 HE 0557-4840 Pe* 05 58 39.2660594064 -48 39 56.890252404   16.16 15.45 14.991   CEMP-no 84 0
13 HE 1012-1540 Pe* 10 14 53.4753516864 -15 55 53.172437448     14.04     CEMP-no 34 0
14 UCAC3 215-112497 Pe* 10 29 15.1489854864 +17 29 27.924626724         15.98 ~ 102 0
15 SDSS J103556.11+064143.9 Pe* 10 35 56.1158830560 +06 41 44.004045912           CEMP-no 23 0
16 HE 1133-0555 Pe* 11 36 11.7638171376 -06 11 43.119652740   16.063 15.427 15.030 14.639 CEMP-no 6 0
17 HE 1150-0428 Pe* 11 53 06.6090188016 -04 45 03.485197944     14.91     CEMP-no 28 0
18 HE 1201-1512 Pe* 12 03 37.0449862176 -15 29 33.236334924   14.2       CEMP-no 19 0
19 HE 1300+0157 Pe* 13 02 56.2443901392 +01 41 52.080457056   14.536 14.11 13.678 13.261 CEMP-no 41 0
20 BPS BS 16929-0005 Pe* 13 03 29.4751261824 +33 51 09.242978436 14.109 14.228 13.610 13.208 12.766 CEMP-no 35 0
21 HE 1300-0641 Pe* 13 03 34.1329557000 -06 57 20.869557192     14.804   13.929 CEMP-no 15 0
22 HE 1302-0954 Pe* 13 04 58.2130607664 -10 10 10.583620608   14.5       CEMP-no 6 0
23 2MASS J13132688-0019415 Pe* 13 13 26.8884339336 -00 19 41.336280264           CEMP-no 27 0
24 BPS CS 22877-0001 Pe* 13 13 55.3726775760 -12 11 41.666054388   12.78 12.38 11.695 11.218 CEMP-no 38 0
25 HE 1327-2326 Pe* 13 30 05.9394958608 -23 41 49.699340844 13.761 14.01 13.55 13.50 12.803 CEMP-no 232 0
26 HE 1410+0213 Pe* 14 13 06.5623389120 +01 59 21.911258400   14.29 13.25 12.734 12.297 CEMP-no 22 0
27 HE 1506-0113 Pe* 15 09 14.2925716632 -01 24 56.730524328   15.4       CEMP-no 23 0
28 HE 1523-0901 Pe* 15 26 01.0697532504 -09 11 38.885639784   12.37 11.50 10.476 9.863 CEMP 71 0
29 BPS CS 22878-0027 Pe* 16 37 35.8437123792 +10 22 07.754788668   14.86 14.35 14.45   CEMP-no 24 0
30 SDSS J174259.67+253135.8 Pe* 17 42 59.6805182976 +25 31 35.892397632           CEMP-no 20 0
31 BPS CS 29498-0043 Pe* 21 03 52.1197651440 -29 42 50.344181712   14.8 13.72 13.013 12.406 CEMP-no 91 0
32 BPS CS 29502-0092 Pe* 22 22 35.9982138384 -01 38 27.620508552   12.64 11.87 11.365 10.862 CEMP-no 51 0
33 CD-24 17504 Pe* 23 07 20.2534619736 -23 52 35.954286096   12.51 12.18     CEMP-no 84 0
34 HE 2318-1621 Pe* 23 21 21.5631300312 -16 05 05.628387156   13.38 12.73 12.67   CEMP-no 14 0
35 HE 2323-0256 Pe* 23 26 29.8073738880 -02 39 58.036383180   15.12 14.36   13.358 CEMP-no 175 0
36 HE 2356-0410 Pe* 23 59 13.1419841280 -03 53 48.220213560   14.39 13.60 13.164 12.713 CEMP-no 84 0

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2023.02.04-09:59:47

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