2007A&A...464..601P

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 Query : 2007A&A...464..601P

2007A&A...464..601P - Astronomy and Astrophysics, volume 464, 601-607 (2007/3-3)

Beryllium abundance in turn-off stars of NGC 6752.

PASQUINI L., BONIFACIO P., RANDICH S., GALLI D., GRATTON R.G. and WOLFF B.

Abstract (from CDS):

To measure the beryllium abundance in two TO stars of the Globular Cluster NGC 6752, one oxygen rich and sodium poor, the other presumably oxygen poor and sodium rich. Be abundances in these stars are used to put on firmer grounds the hypothesis of Be as cosmochronometer and to investigate the formation of Globular Clusters. We present near UV spectra with resolution R∼45000 obtained with the UVES spectrograph on the 8.2m VLT Kueyen telescope, analysed with spectrum synthesis based on plane parallel LTE model atmospheres. Be is detected in the O rich star with log(Be/H)=-12.04±0.15, while Be is not detected in the other star for which we obtain the upper limit log(Be/H)←12.2. A large difference in nitrogen abundance (1.6dex) is found between the two stars. The Be measurement is compatible with what found in field stars with the same [Fe/H] and [O/H]. The Be age'' of the cluster is found to be 13.3Gyr, in excellent agreement with the results from main sequence fitting and stellar evolution. The presence of Be confirms the results previously obtained for the cluster NGC 6397 and supports the hypothesis that Be can be used as a clock for the early formation of the Galaxy. Since only an upper limit is found for the star with low oxygen abundance, we cannot decide between competing scenarios of Globular Cluster formation, but we can exclude that polluted'' stars are substantially younger than unpolluted'' ones. We stress that the Be test might be the only measurement capable of distinguishing between these scenarios.

Journal keyword(s): stars: abundances - stars: globular clusters: individual: NGC 6752 - stars: late-type - stars: individual : Beryllium

Full paper

 Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20   5.78 4.09     ~ 3782 0
2 IC 2391 OpC 08 41 10 -52 59.5           ~ 796 0
3 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 1911 0
4 NGC 6752 GlC 19 10 52.11 -59 59 04.4           ~ 1927 0
5 Cl* NGC 6752 GVS 4428 * 19 10 59.8758025704 -60 02 17.122587576     17.142     ~ 10 0
6 Cl* NGC 6752 GVS 4907 * 19 11 22.87 -60 03 57.6     17.199     ~ 8 0
7 Cl* NGC 6752 GVS 200613 * 19 11 35.7511814976 -59 58 02.021234016           ~ 11 0

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2023.02.02-19:01:42