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


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.14CEST14:27:40

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 - 2019
#notes
1 C* 3221 Pe* 00 20 21.5999105195 +01 12 06.814621800   12.991 11.66 10.773 10.186 CEMP-s 16 0
2 BPS CS 30324-0063 Pe* 00 22 44.8620944430 -17 24 29.142325967   13.824 12.887     CEMP-no 12 0
3 BPS CS 29527-0015 Pe* 00 29 10.6813715074 -19 10 07.306464364   14.61 14.24     CEMP-no 50 0
4 BPS CS 22166-0016 Pe* 00 58 23.8414780886 -14 47 06.881569381   13.34 12.75 12.324 11.898 ~ 17 0
5 HE 0107-5240 Pe* 01 09 29.1554552993 -52 24 34.203535506   15.89 15.07 15.10 14.283 CEMP-no 224 0
6 BPS CS 31082-0001 Pe* 01 29 31.1311330115 -16 00 45.496485322 12.527 12.427 11.642 11.189 10.713 ~ 237 0
7 HE 0219-1739 Pe* 02 21 41.2959105494 -17 25 37.032701370   15.85 14.10 14.035 13.444 CEMP-no 8 0
8 BD+44 493 Pe* 02 26 49.7388403813 +44 57 46.526253277   9.63 9.11     CEMP-no 81 0
9 2MASS J02362978-0330060 Pe* 02 36 29.7931232841 -03 30 06.028585140   15.867 15.430 15.171 14.818 CEMP-no 26 0
10 SMSS J031300.36-670839.3 Pe* 03 13 00.3747490864 -67 08 39.336567558           CEMP-no 79 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 39.2661082631 -48 39 56.890701762   16.16 15.45 14.991   CEMP-no 79 0
13 HE 1012-1540 Pe* 10 14 53.4754858508 -15 55 53.171904692     14.04     CEMP-no 29 0
14 UCAC3 215-112497 Pe* 10 29 15.1491308300 +17 29 27.926665478         15.98 ~ 85 0
15 SDSS J103556.11+064143.9 Pe* 10 35 56.1164062654 +06 41 44.009615054           CEMP-no 20 0
16 2MASS J11361175-0611431 Pe* 11 36 11.7636415660 -06 11 43.119640336   16.063 15.427 15.030 14.639 CEMP-no 5 0
17 UCAC4 427-054095 Pe* 11 53 06.6089448606 -04 45 03.484251112     14.91     CEMP-no 24 0
18 HE 1201-1512 Pe* 12 03 37.0450878463 -15 29 33.235237621   14.2       CEMP-no 15 0
19 HE 1300+0157 Pe* 13 02 56.2444113387 +01 41 52.080881619   14.536 14.11 13.678 13.261 CEMP-no 39 0
20 BPS BS 16929-0005 Pe* 13 03 29.4750923367 +33 51 09.243677482 14.109 14.228 13.610 13.208 12.766 CEMP-no 32 0
21 HE 1300-0641 Pe* 13 03 34.1329709575 -06 57 20.869199156     14.804   13.929 CEMP-no 13 0
22 2MASS J13045819-1010106 Pe* 13 04 58.2130874769 -10 10 10.583993517   14.5       CEMP-no 5 0
23 2MASS J13132688-0019415 Pe* 13 13 26.8883961320 -00 19 41.335927067           CEMP-no 24 0
24 BPS CS 22877-0001 Pe* 13 13 55.3726645896 -12 11 41.664182839   12.78 12.38 11.695 11.218 CEMP-no 32 0
25 HE 1327-2326 Pe* 13 30 05.9395582011 -23 41 49.699027289 13.761 14.01 13.55 13.50 12.803 CEMP-no 209 0
26 HE 1410+0213 Pe* 14 13 06.5623968167 +01 59 21.912907907   14.29 13.25 12.734 12.297 dC-H 21 0
27 HE 1506-0113 Pe* 15 09 14.2926751829 -01 24 56.730409770   15.4       CEMP-no 19 0
28 TYC 5594-576-1 Pe* 15 26 01.0697794752 -09 11 38.882076152   12.37 11.50 10.476 9.863 ~ 58 0
29 BPS CS 22878-0027 Pe* 16 37 35.8437255100 +10 22 07.754675906   14.86 14.35 14.45   ~ 22 0
30 SDSS J174259.67+253135.8 Pe* 17 42 59.6806116319 +25 31 35.890539509           CEMP-no 18 0
31 BPS CS 29498-0043 Pe* 21 03 52.1197489072 -29 42 50.344264361   14.8 13.72 13.013 12.406 CEMP-no 84 0
32 BPS CS 29502-0092 Pe* 22 22 35.9981441327 -01 38 27.624102360   12.64 11.87 11.365 10.862 CEMP-no 42 0
33 CD-24 17504 Pe* 23 07 20.2536159873 -23 52 35.956455668   12.51 12.18     CEMP-no 81 0
34 HE 2318-1621 Pe* 23 21 21.5631896741 -16 05 05.631099048   13.38 12.73 12.67   CEMP-no 7 0
35 HE 2323-0256 Pe* 23 26 29.8073543039 -02 39 58.037206596   15.12 14.36   13.358 CEMP-no 166 0
36 HE 2356-0410 Pe* 23 59 13.1417869434 -03 53 48.220053208   14.39 13.60 13.164 12.713 CEMP-no 78 0

    Equat.    Gal    SGal    Ecl

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2019.10.14-14:27:40

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