2003A&A...402..985Y


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST22:56:55

2003A&A...402..985Y - Astronomy and Astrophysics, volume 402, 985-1001 (2003/5-2)

Mg isotopic ratios in giant stars of the globular cluster NGC 6752.

YONG D., GRUNDAHL F., LAMBERT D.L., NISSEN P.E. and SHETRONE M.D.

Abstract (from CDS):

Mg isotopic abundance ratios are measured in 20 bright red giants in globular cluster NGC 6752 based on very high-resolution (R∼110000), high signal-to-noise spectra obtained with UVES on the VLT. There is a considerable spread in the ratio 24Mg:25Mg:26Mg with values ranging from 53:9:39 to 83:10:7. We measured the abundances of O, Na, Mg, Al, and Fe combining our sample with 21 RGB bump stars (Grundahl et al., 2002A&A...385L..14G). The abundances of the samples are consistent and exhibit the usual anticorrelations between O-Na and Mg-Al. A positive correlation is found between 26Mg and Al, a mild anticorrelation is found between 24Mg and Al, while no correlation is found between 25Mg and Al. None of the elemental or isotopic abundances show a dependence on evolutionary status and, as shown by Gratton et al. (2001A&A...369...87G), the abundance variations exist even in main sequence stars. This strongly suggests that the star-to-star abundance variations are a result of varying degrees of pollution with intermediate mass AGB stars being likely polluters. Consideration of the extremes of the abundance variations provides the composition of the ambient material and the processed material. In the least contaminated stars (lowest Na and Al and highest O and Mg abundances), we infer a Mg isotopic ratio around 80:10:10 and a composition ([O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe]) ≃ (0.6, -0.1, 0.5, 0.0). In the most polluted stars, we find a Mg isotopic ratio around 60:10:30 and a composition ([O/Fe], [Na/Fe], [Mg/Fe], [Al/Fe]) ≃ (-0.1, 0.6, 0.3, 1.2). Even for the least polluted stars, the abundances of 25Mg and 26Mg relative to 24Mg are considerably higher than predicted for ejecta from Z=0 supernovae. Zero metallicity AGB stars may be responsible for these higher abundances. Our measured Mg isotopic ratios reveal another layer to the globular cluster star-to-star abundance variations that demands extensions of our present theoretical knowledge of stellar nucleosynthesis by giant stars.

Abstract Copyright:

Journal keyword(s): galaxies: clusters: general - galaxies: clusters: individual: NGC 6752 - stars: abundances - stars: evolution - stars: fundamental parameters

Nomenclature: Table 1: Cl* NGC 6752 MG NN N=17 among (Nos 0-25).

Simbad objects: 23

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Number of rows : 23

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 V* TY Vir LP* 11 51 50.1113597773 -05 45 44.181741901   9.668 7.97 7.57   G3Ibp 110 0
2 HD 141531 PM* 15 49 16.4995136367 +09 36 42.408762912   10.31 9.08 8.720   M1V 60 0
3 HD 166197 V* 18 10 55.3482376641 -33 48 00.250805215 5.16 6.02 6.16     B2II/III 46 0
4 NGC 6752 68 * 19 10 27.8250410588 -59 59 49.279458493   13.08 12.01     ~ 9 0
5 NGC 6752 59 * 19 10 32.2388076417 -59 57 07.287990595   12.58 10.887     M 32 0
6 Cl* NGC 6752 CS 3 * 19 10 38.3082058963 -60 04 14.038404660   12.75 11.49     ~ 23 0
7 Cl* NGC 6752 MG 9 * 19 10 40 -59 58.2     11.52     ~ 4 0
8 Cl* NGC 6752 GA 88 * 19 10 40 -59 54.6     10.52     ~ 1 0
9 Cl* NGC 6752 MG 4 * 19 10 42.451272 -59 59 54.79008     11.02 10.72   ~ 4 0
10 2MASS J19104617-5956267 RG* 19 10 46.1704140923 -59 56 26.704769547   13.40 12.24     ~ 11 0
11 Cl* NGC 6752 MG 5 * 19 10 48.758616 -59 59 38.29308     11.03     ~ 4 0
12 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1807 0
13 NGC 6752 45 * 19 10 53.2458137870 -59 57 15.308961089   12.78 11.54     ~ 12 0
14 2MASS J19105326-6002037 RG* 19 10 53.2772614549 -60 02 03.674240914   13.06 12.060     ~ 23 0
15 NGC 6752 44 * 19 10 57.3796160500 -59 57 03.652402548   12.94 11.60     ~ 7 0
16 2MASS J19110109-5957226 RG* 19 11 01.1113286194 -59 57 22.632740331   12.88 11.68     ~ 13 0
17 NGC 6752 12 * 19 11 03.0385257037 -60 01 48.905572074   12.60 11.245     K 27 0
18 NGC 6752 31 * 19 11 11.2979674851 -59 59 55.429811496   12.52 10.833     M 32 0
19 2MASS J19111438-6000322 RG* 19 11 14.3923849338 -60 00 32.225033415   13.006 11.867     ~ 28 0
20 NGC 6752 18 * 19 11 16.8664380693 -60 03 10.617500026   12.32 10.99     ~ 6 0
21 2MASS J19111945-6000347 RG* 19 11 19.4661277471 -60 00 34.730459562   13.27 12.195     ~ 21 0
22 Cl* NGC 6752 BUON 708 * 19 11 31 -59 54.6     10.58     ~ 3 0
23 Cl* NGC 6752 BUON 702 * 19 11 31 -59 54.6     10.83     ~ 4 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-22:56:55

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