2016A&A...587A..42P


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.08CET20:02:30

2016A&A...587A..42P - Astronomy and Astrophysics, volume 587A, 42-42 (2016/3-1)

New determination of abundances and stellar parameters for a set of weak G-band stars.

PALACIOS A., JASNIEWICZ G., MASSERON T., THEVENIN F., ITAM-PASQUET J. and PARTHASARATHY M.

Abstract (from CDS):

Weak G-band (wGb) stars are a very peculiar class of red giants; they are almost devoided of carbon and often present mild lithium enrichment. Despite their very puzzling abundance patterns, very few detailed spectroscopic studies existed up to a few years ago, which prevented any clear understanding of the wGb phenomenon. We recently proposed the first consistent analysis of published data for a sample of 28 wGb stars and were able to identify them as descendants of early A-type to late B-type stars, although we were not able to conclude on their evolutionary status or the origin of their peculiar abundance pattern. Using new high-resolution spectra, we present the study of a new sample of wGb stars with the aim of homogeneously deriving their fundamental parameters and surface abundances for a selected set of chemical species that we use to improve our insight on this peculiar class of objects. We obtained high-resolution and high signal-to-noise spectra for 19 wGb stars in the southern and northern hemisphere that we used to perform consistent spectral synthesis to derive their fundamental parameters and metallicities, as well as the spectroscopic abundances for Li, C, 12C/13C, N, O, Na, Sr, and Ba. We also computed dedicated stellar evolution models that we used to determine the masses and to investigate the evolutionary status and chemical history of the stars in our sample. We confirm that the wGb stars are stars with initial masses in the range 3.2 to 4.2M. We suggest that a large fraction could be mildly evolved stars on the subgiant branch currently undergoing the first dredge-up, while a smaller number of stars are more probably in the core He burning phase at the clump. After analysing their abundance pattern, we confirm their strong nitrogen enrichment anti-correlated with large carbon depletion, characteristic of material fully processed through the CNO cycle to an extent not known in evolved intermediate-mass stars in the field and in open clusters. However, we demonstrate here that such a pattern is very unlikely owing to self-enrichment. In the light of the current observational constraints, no solid self-consistent pollution scenario can be presented either, leaving the wGb puzzle largely unsolved.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: carbon - stars: chemically peculiar - stars: late-type - stars: evolution

VizieR on-line data: <Available at CDS (J/A+A/587/A42): tablea1.dat table1.dat table2.dat table3.dat table5.dat table7.dat>

Simbad objects: 31

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Number of rows : 31

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 HD 1847 * 00 23 08.2044863011 +48 12 36.699310700   9.37 9.31     A0 7 0
2 HD 4996 * 00 52 43.6300107814 +52 16 41.963363706   7.98 7.89     A0 8 0
3 HD 5643 * 00 57 57.9278110350 -20 40 34.175175274   8.14 7.75     F0/2V 26 0
4 HD 6772 * 01 09 16.1185706358 +52 36 10.355949429 9.390 9.280 9.000     A2 8 0
5 HD 8259 * 01 16 42.8170219283 -81 32 27.210398321   9.974 9.151     G8III 10 0
6 HD 7814 ** 01 17 43.204 -12 20 35.62           F3/7+F 8 0
7 HD 9180 PM* 01 30 33.9457903077 +05 22 15.795062444   9.08 8.52     G0V 24 0
8 HD 9495 * 01 33 25.1701930556 +14 07 04.088988347   9.99 9.52     G5 3 0
9 HD 16068 * 02 36 52.7996071580 +55 54 55.441758278   9.18 7.45     K3II-III 27 0
10 Cl Trumpler 2 OpC 02 36 53 +55 54.9           ~ 90 0
11 HD 18474 * 02 59 49.7890668899 +47 13 14.556905395   6.348 5.485     G5:III:CN-3CH-2Hdel-1 99 0
12 HD 49960 * 06 49 40.5443271213 -31 15 32.847704637 10.22 9.37 8.35 7.54 6.95 K2/3IIIp+(G) 16 0
13 HD 56438 * 07 14 36.4080079540 -47 08 05.811163538 10.01 9.14 8.10 7.23 6.59 K0.5IIIbCH-0.5 23 0
14 HD 67728 ** 08 08 37.6488621580 -19 50 23.658888152 9.66 8.66 7.54 6.67 6.07 G8/K0III 25 0
15 HD 78146 * 09 05 44.2118724301 -28 04 59.417711048 10.82 9.72 8.56 7.65 7.00 K1IIICNIV/Vp 26 0
16 HD 82595 * 09 31 57.7827266621 -36 51 34.325149605 10.15 9.21 8.18 7.36 6.80 K2II/III 19 0
17 NGC 3144 G 10 15 32.238 +74 13 12.94   14.3       ~ 21 0
18 HD 91805 PM* 10 35 10.4124514249 -43 39 52.509421924 7.75 7.04 6.10 5.32 5.32 G7IIICH-3 41 0
19 HD 94956 * 10 57 23.9921318569 -29 16 50.726892100 10.14 9.41 8.45 7.64 7.12 K0IIICNVp 26 0
20 HD 102851 * 11 50 16.3992517590 -51 28 14.305076235 10.74 9.84 8.77 7.92 7.31 K0/1IIICNVp 15 0
21 HD 119256 * 13 43 36.2766562672 -57 35 23.909458542 9.39 8.44 7.31 6.39 5.72 K1III 16 1
22 HD 120170 * 13 47 58.7913528810 -08 47 22.711758612 10.64 9.97 9.04 9.04 9.04 G8V 21 0
23 HD 120213 * 13 55 38.8749383943 -82 39 58.287765471 8.98 7.39 5.94 5.94 5.94 K2III:CN-1CH-2.5 23 0
24 HD 124721 * 14 16 24.5578371405 -45 11 23.160787810 11.73 10.89 9.85 9.85 9.85 K1/2(III) 15 0
25 HD 146116 * 16 14 38.3964493611 -00 23 55.500363421 9.65 8.75 7.68 6.83 6.20 G7IIICH-2Hdel-0.5 17 0
26 GAL 000.0+00.0 gam 17 45 39.60213 -29 00 22.0000           ~ 12014 0
27 HD 165462 * 18 06 07.4276998738 -00 26 46.057195192 8.16 7.40 6.34     G9IIICH-3 51 0
28 HD 166208 SB* 18 07 28.7432061157 +43 27 42.749010239   5.915 4.997     G8IIICN-1CH-3 144 0
29 HD 165634 * 18 08 04.9798155 -28 27 25.531664 6.26 5.51 4.56 3.85 3.32 G7:IIIbCN-1CH-3.5HK+1 93 0
30 HD 204046 * 21 26 54.1298388309 -33 54 35.665983739   10.10 9.05     G8/K0IIICNVp 10 0
31 HD 207774 * 21 51 33.5833804025 -07 24 14.305415055   9.85 8.90     G8III 12 0

    Equat.    Gal    SGal    Ecl

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2021.03.08-20:02:30

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