The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters

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dc.creatorGratton, R. G.
dc.creatorBonifacio, P.
dc.creatorBragaglia, A.
dc.creatorCarretta, E.
dc.creatorCastellani, V.
dc.creatorCenturion, M.
dc.creatorChieffi, A.
dc.creatorClaudi, R.
dc.creatorClementini, G.
dc.creatorD'Antona, F.
dc.creatorDesidera, S.
dc.creatorFrancois, P.
dc.creatorGrundahl, F.
dc.creatorLucatello, S.
dc.creatorMolaro, P.
dc.creatorPasquini, L.
dc.creatorSneden, C.
dc.creatorSpite, F.
dc.creatorStraniero, O.
dc.date2000-12-21
dc.date.accessioned2026-07-07T10:47:17Z
dc.date.available2026-07-07T10:47:17Z
dc.descriptionHigh dispersion spectra (R>40,000) for a quite large number of stars at the main sequence turn-off and at the base of the subgiant branch in NGC6397 and NGC6752 were obtained with the UVES on Kueyen (VLT UT2). The [Fe/H] values we found are -2.03+/-0.02+/-0.04 and -1.42+/-0.02+/-0.04 for NGC6397 and NGC6752 respectively, where the first error bars refer to internal errors and the second ones to systematic errors. In both clusters the [Fe/H] obtained for TO-stars agree perfectly (within a few per cents) with that obtained for stars at the base of the RGB. The [O/Fe]=0.21+/-0.05 value we obtain for NGC6397 is quite low, but it agrees with previous results obtained for giants in this cluster; also, the star-to-star scatter in both O and Fe is very small, indicating that this small mass cluster is chemically very homogenous. On the other side, our results show clearly and for the first time that the O-Na anticorrelation (up to now seen only for stars on the red giant branches of globular clusters) is present among unevolved stars in the globular cluster NGC6752, a more massive cluster than NGC6397. A similar anticorrelation is present also for Mg and Al, and C and N. It is very difficult to explain the observed Na-O, and Mg-Al anticorrelation in NGC6752 stars by a deep mixing scenario; we think it requires some non internal mechanism.
dc.description20 pages, A&A Latex, including 7 .ps figures, tex-macro aa.cls, uses psfig.tex. submitted to Astronomy & Astrophysics
dc.identifierhttps://arxiv.org/abs/astro-ph/0012457
dc.identifierhttp://arxiv.org/abs/astro-ph/0012457
dc.identifierAstron.Astrophys.369:87-98,2001
dc.identifierdoi:10.1051/0004-6361:20010144
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/183483
dc.subjectAstrophysics
dc.titleThe O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters
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