2011A&A...534A..29D


Query : 2011A&A...534A..29D

2011A&A...534A..29D - Astronomy and Astrophysics, volume 534A, 29-29 (2011/10-1)

Chemical enrichment mechanisms in ω Centauri: clues from neutron-capture elements.

D'ORAZI V., GRATTON R.G., PANCINO E., BRAGAGLIA A., CARRETTA E., LUCATELLO S. and SNEDEN C.

Abstract (from CDS):

In the complex picture of multiple stellar populations in globular clusters (GCs), a special role is played by NGC 5139 (ω Centauri). At variance with the majority of GCs, ω Cen exhibits significant star-to-star variations in metallicity and in relative neutron-capture element abundance ratios with respect to Fe, along with split evolutionary sequences as revealed from colour-magnitude diagrams. Combining information from photometry and spectroscopy, several studies suggested that an age spread of several Gyr has to be invoked to explain (at least partially) some of the observed features. However, a comprehensive understanding of the formation, evolution and chemical enrichment processes is still not at hand. Relatively metal-rich ω Cen stars display neutron-capture abundance distributions dominated by contributions from the s-process, but it is not clear what roles have been played by the so-called main and weak s-process components in generating these abundances. To gain better insight into this question we derived lead (Pb) abundances for several ω Cen cluster members, because this element can only be produced by the main s-process. We analysed high-resolution UVES@VLT spectra of a sample of twelve red-giant branch stars, deriving abundances of Pb and also of Y, Zr, La, Ce, Eu, and the C+N+O sum. Spectral synthesis was applied to all features, taking into account isotopic shifts and/or hyperfine structure as needed. We measured for the first time the Pb content in ω Cen, discovering a clear hint for a Pb production occurring at [Fe/H]>-1.7dex. Our data suggest that the role of the weak component in the production of s-process elements is negligible. Moreover, evidence gathered from the abundances of other elements indicates that the main component occurring in this GC is peculiar and shifted towards higher mass polluters than the standard one.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: Population II - globular clusters: individual: {omega} Centauri (NGC 5139)

Simbad objects: 21

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Number of rows : 21
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1408 0
2 NGC 5139 159 RG* 13 25 17.5229869368 -47 24 26.555561460   13.369 12.004 11.704 10.45 ~ 40 0
3 2MASS J13254217-4733437 RG* 13 25 42.1720570392 -47 33 43.801448904 16.41 14.770 13.358   12.005 ~ 17 0
4 NGC 5139 256 RG* 13 25 53.7674977320 -47 28 12.181831032   13.481 12.251   10.97 ~ 28 0
5 NGC 5139 243 RG* 13 26 04.3785491112 -47 25 00.924967128   13.598 12.107   10.714 ~ 15 0
6 2MASS J13261954-4716345 RG* 13 26 19.5473955312 -47 16 34.505962392   13.32 12.15     ~ 45 0
7 NGC 5139 92 RB? 13 26 26.0169779088 -47 30 13.626938772   13.377 11.830   10.280 ~ 10 0
8 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3378 0
9 NGC 5139 2118 RG* 13 26 49.9504136328 -47 36 41.876365788   14.374 13.086   12.096 ~ 10 0
10 HD 116811 RG* 13 26 53.3609740560 -47 36 35.006770080 15.91 13.880 12.267 12.09 10.837 A 18 0
11 2MASS J13270238-4726059 RG* 13 27 02.3933646408 -47 26 06.018499392   13.593 12.430   11.15 ~ 19 0
12 AP J13270546-4724369 RB? 13 27 05.4717788856 -47 24 37.016838612   14.511 13.030   11.555 K5: 15 0
13 2MASS J13270563-4731049 RG* 13 27 05.6462065512 -47 31 04.922839776 16.38 14.540 13.079   11.567 K5: 16 0
14 NGC 5139 321 RB? 13 27 17.0221641240 -47 29 06.087168024   13.962 12.559     ~ 9 0
15 * alf Boo RG* 14 15 39.67207 +19 10 56.6730 2.46 1.18 -0.05 -1.03 -1.68 K1.5IIIFe-0.5 2307 1
16 NGC 6522 GlC 18 03 34.08 -30 02 02.3           ~ 517 0
17 M 22 GlC 18 36 23.94 -23 54 17.1           ~ 1356 0
18 NGC 6705 OpC 18 51 03.8 -06 16 19   6.32 5.8     ~ 408 0
19 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 1052 0
20 NGC 6752 GlC 19 10 52.11 -59 59 04.4           ~ 1974 0
21 M 15 GlC 21 29 58.33 +12 10 01.2           ~ 3114 0

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2023.11.28-10:03:56

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