2004A&A...414..931A


C.D.S. - SIMBAD4 rel 1.7 - 2020.01.24CET14:32:23

2004A&A...414..931A - Astronomy and Astrophysics, volume 414, 931-942 (2004/2-2)

The evolution of the C/O ratio in metal-poor halo stars.

AKERMAN C.J., CARIGI L., NISSEN P.E., PETTINI M. and ASPLUND M.

Abstract (from CDS):

We report new measurements of carbon and oxygen abundances in 34 F and G dwarf and subgiant stars belonging to the halo population and spanning a range of metallicity from [Fe/H]=-0.7 to -3.2. The survey is based on observations of four permitted lines of CI near 9100Å and the OIλ7774 triplet, all recorded at high signal-to-noise ratios with the UVES echelle spectrograph on the ESO VLT. The line equivalent widths were analysed with the 1D, LTE, MARCS model atmosphere code to deduce C and O abundances; corrections due to non-LTE and 3D effects are discussed. When combined with similar published data for disk stars, our results confirm the metallicity dependence of the C/O ratio known from previous stellar and interstellar studies: C/O drops by a factor of ∼3-4 as O/H decreases from solar to ∼1/10 solar. Analysed within the context of standard models for the chemical evolution of the solar vicinity, this drop results from the metallicity dependence of the C yields from massive stars with mass loss, augmented by the delayed release of C from stars of low and intermediate mass. The former is, however, always the dominant factor. Our survey has also uncovered tentative evidence to suggest that, as the oxygen abundance decreases below [O/H]=-1, [C/O] may not remain constant at [C/O]=-0.5, as previously thought, but increase again, possibly approaching near-solar values at the lowest metallicities ([O/H]≲-3). With the current dataset this is no more than a 3σ effect and it may be due to metallicity-dependent non-LTE corrections to the [C/O] ratio which have not been taken into account. However, its potential importance as a window on the nucleosynthesis by Population III stars is a strong incentive for future work, both observational and theoretical, to verify its reality.

Abstract Copyright:

Journal keyword(s): stars: abundances - Galaxy: abundances - Galaxy: evolution - Galaxy: halo

Simbad objects: 34

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Number of rows : 34

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 Ross 892 PM* 10 27 24.2462412761 +01 24 00.192254880   11.55   10.8   sdF8 57 0
2 BD-13 3442 Pe* 11 46 50.6526364381 -14 06 43.453858029   10.662 10.274     CEMP 89 0
3 HD 103723 PM* 11 56 36.0250188318 -21 25 09.826660968   10.554 10.091     F5/6V 67 0
4 HD 105004 PM* 12 05 24.8526214531 -26 35 43.746369085   10.96 10.39     F9 91 0
5 BD-04 3208 PM* 12 07 15.0719832426 -05 44 01.609304815   10.40 9.99     A7 132 0
6 Ross 453 PM* 12 10 55.7739013257 +00 23 54.336245712   11.53   10.9   F2 96 0
7 HD 106038 PM* 12 12 01.3690548564 +13 15 40.620671155 10.45 10.630 10.162 9.851 9.539 F6wl 167 0
8 HD 108177 PM* 12 25 34.9568983381 +01 17 02.259993860 9.87 10.09 9.66 9.21 8.89 F0V 229 0
9 HD 110621 PM* 12 43 43.2212558894 -44 40 31.556081512   10.34 9.92     Fpw 64 0
10 Wolf 1492 Pe* 13 40 02.4921790616 -00 02 18.750321114 11.601 11.832 11.451 11.184 10.892 sdF0: 258 0
11 HD 121004 PM* 13 53 58.1163515488 -46 32 19.526169178   10.112 9.522     G2V 124 0
12 Ross 841 Pe* 14 02 30.0901582051 -05 39 05.181328144   11.508 11.149 10.866 10.576 sdA3 135 0
13 Wolf 550 SB* 14 50 07.8015005617 +00 50 27.177034317   11.47   10.8   sd:F5 72 0
14 HD 140283 Pe* 15 43 03.0967798658 -10 56 00.595803430 7.508 7.711 7.212 6.63 8.21 F9VkA5mA1 848 0
15 BD+08 3095 PM* 15 50 58.9335540844 +08 25 23.722428557   10.60   9.8   G2 70 0
16 HD 146296 PM* 16 21 11.3147049208 -71 17 13.024512360   10.37 9.77     G3V 37 0
17 HD 148816 PM* 16 30 28.4586643435 +04 10 41.603810207 7.75 7.81 7.28 6.82 6.49 F7V 279 0
18 BD+02 3375 PM* 17 39 45.5950264172 +02 24 59.607595293 10.18 10.40 9.92 9.47 9.12 A5 180 0
19 HD 160617 PM* 17 42 49.3235999900 -40 19 15.505712142   9.18 8.73 8.394 8.065 G0 182 0
20 HD 179626 PM* 19 13 20.7187369501 -00 35 42.340961173   9.701 9.187 8.844 8.489 F5V 109 0
21 HD 181743 PM* 19 23 42.7454549059 -45 04 56.915607302   10.13 9.71     F4 96 0
22 CD-42 14278 PM* 19 32 19.1472126350 -42 12 43.711550816   10.76 10.29     F5Vwl 31 0
23 HD 188031 PM* 19 54 58.6571400220 -42 38 43.396854578   10.54 10.17     F0V 58 0
24 G 24-3 PM* 20 05 44.3170613889 +04 02 52.811312960   10.92   10.2   sdF8 77 0
25 HD 193901 PM* 20 23 35.8472360557 -21 22 14.228814044 9.08 9.22 8.67 8.17 7.87 F7V 254 0
26 HD 340279 PM* 20 24 45.4127587189 +25 03 07.108270663   11.23   10.7   A5 90 0
27 HD 194598 PM* 20 26 11.9185966774 +09 27 00.429262518 8.62 8.82 8.34 7.90 7.56 F8 283 0
28 LP 815-43 PM* 20 38 13.2997980664 -20 26 10.852305467   11.31 10.72     ~ 64 0
29 CD-30 18140 PM* 20 44 06.2871219229 -30 00 07.598765502   10.326 9.932     F8 73 0
30 CD-35 14849 PM* 21 33 49.75243 -35 26 14.2322   10.95 10.56 10.59   B8 62 0
31 BD+17 4708 SB* 22 11 31.3751899315 +18 05 34.158392398 9.73 9.91 9.46 9.03 8.70 sdF8 530 0
32 BD+07 4841 PM* 22 18 36.5061308735 +08 26 44.960669943   10.84   10.1   G0 96 0
33 HD 215801 PM* 22 48 29.4256501613 -46 03 50.539434337   10.46 10.05     F0w 56 0
34 BD+02 4651 PM* 23 19 40.4501666092 +03 22 16.692679350   10.67   9.9   sdF6 97 0

    Equat.    Gal    SGal    Ecl

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2020.01.24-14:32:24

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