2006A&A...458..777K


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.01CET21:50:02

2006A&A...458..777K - Astronomy and Astrophysics, volume 458, 777-788 (2006/11-2)

Medium resolution spectroscopy in ω Centauri: abundances of 400 subgiant and turn-off region stars.

KAYSER A., HILKER M., RICHTLER T. and WILLEMSEN P.G.

Abstract (from CDS):

Medium resolution spectra of more than 400 subgiant and turn-off region stars in ω Centauri were analysed. The observations were performed at the VLT/Paranal with FORS2/MXU. In order to determine the metallicities of the sample stars, we defined a set of line indices (mostly iron) adjusted to the resolution of our spectra. The indices as determined for ωCen were then compared to line indices from stars in the chemically homogeneous globular cluster M55, in addition to standard stars and synthetic spectra. The uncertainties in the derived metallicities are of the order of ±0.2dex. Our study confirms the large variations in iron abundances found on the giant branch in earlier studies (-2.2<[Fe/H]←0.7dex). In addition, we studied the α-element and CN/CH abundances. Stars of different metallicity groups not only show distinct ages (Hilker et al., 2004A&A...422L...9H), but also different behaviours in their relative abundances. The α abundances increase smoothly with increasing metallicity resulting in a flat [α/Fe] ratio over the whole observed metallicity range. The combined CN+CH abundance increases smoothly with increasing iron abundance. The most metal-rich stars are CN-enriched. In a CN vs. CH plot, though, the individual abundances divide into CN- and CH-rich branches. The large abundance variations observed in our sample of (unevolved) subgiant branch stars most probably have their origin in the pre-enriched material rather than in internal mixing effects. Together with the age spread of the different sub-populations, our findings favour the formation of ω Centauri within a more massive progenitor.

Abstract Copyright:

Journal keyword(s): stars: abundances - Galaxy: globular clusters: individual: ω Cen - galaxies: dwarf - galaxies: nuclei

Simbad objects: 14

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Number of rows : 14

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 BD-05 2678 ** 08 59 03.3659498292 -06 23 46.177529063   12.515 11.968 11.540 11.159 F7 70 0
2 BD-03 2525 SB* 08 59 10.1107779329 -04 01 36.503689325   10.114 9.648 9.335 9.005 F3 121 0
3 V* DR Oct RS* 10 07 29.5259500705 -85 04 32.989590219   9.42 8.685   7.709 G3V 106 0
4 HD 97916 SB* 11 15 54.2294079228 +02 05 11.982106821 9.50 9.61   8.9   F0V 157 0
5 BD-13 3442 Pe* 11 46 50.6526364381 -14 06 43.453858029   10.662 10.274     CEMP 95 0
6 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3072 0
7 GAL 000.0+00.0 gam 17 45 39.60213 -29 00 22.0000           ~ 11999 0
8 BD-08 4501 PM* 17 47 27.9713460047 -08 46 47.733691581   11.18 10.59     sdF8 114 0
9 HD 179626 PM* 19 13 20.7187369501 -00 35 42.340961173   9.701 9.187 8.844 8.489 F5V 118 0
10 M 55 GlC 19 39 59.71 -30 57 53.1     6.49     ~ 776 0
11 HD 192718 PM* 20 16 38.0858180713 -07 26 37.894785727   8.95 8.41     G3/5V 47 0
12 HD 193901 PM* 20 23 35.8472360557 -21 22 14.228814044 9.08 9.22 8.67 8.17 7.87 F7V 261 0
13 HD 196892 PM* 20 40 49.3803469997 -18 47 33.286582149   8.73 8.23     F6V 112 0
14 HD 205650 PM* 21 37 26.0309417494 -27 38 06.697112156   9.59 9.00     F6V 98 0

    Equat.    Gal    SGal    Ecl

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