Published by
EDP Sciences
EDP Sciences Journals List
Subscriber Authentication Point
Home All issues Volume 407/ 1 Article
Free access
Issue A&A
Volume 407, Number 1, August III 2003
Page(s) 289 - 301
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20030723



A&A 407, 289-301 (2003)
DOI: 10.1051/0004-6361:20030723

The evolution of lithium depletion in young open clusters: NGC 6475

P. Sestito1, S. Randich2, J.-C. Mermilliod3 and R. Pallavicini4

1  Dipartimento di Astronomia, Università di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
2  INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
3  Institut d' Astronomie, Université de Lausanne, 1290, Chavannes-des-Bois, Switzerland
4  INAF/Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 27 February 2003 / Accepted 12 May 2003 )

Abstract
We have carried out a high resolution spectroscopic survey of the 220-250 Myr old cluster NGC 6475 : our main purpose is to investigate Li evolution during the early stages of the Main Sequence. We have determined Li abundances for 33 late F to K-type X-ray selected cluster candidates, extending the samples already available in the literature; for part of the stars we obtained radial and rotational velocities, allowing us to confirm the membership and to check for binarity. We also estimated the cluster metallicity which turned out to be over-solar ( ${\rm [Fe/H]}\rm =+0.14 \pm 0.06$). Our Li analysis evidenced that (i) late F-type stars ( $T_{\rm eff}$ $\ga$ 6000 K) undergo a very small amount of Li depletion during the early phases on the ZAMS; (ii) G-type stars (6000 $\ga$ $T_{\rm eff}$ $\ga$ 5500 K) instead do deplete lithium soon after arrival on the ZAMS. Whereas this result is not new, we show that the time scale for Li depletion in these stars is almost constant between 100 and 600 Myr; (iii) we confirm that the spread observed in early K-type stars in younger clusters has converged by 220 Myr. No constraints can be put on later-type stars. (iv) Finally, we investigate the effect of metallicity on Li depletion by comparing NGC 6475 with the similar age cluster M 34, but we show that the issue remains open, given the uncertain metallicity of the latter cluster. By using the combined NGC 6475+M 34 sample together with the Hyades and the Pleiades, we compare quantitatively Li evolution from the ZAMS to 600 Myr with theoretical predictions of standard models.


Key words: stars: abundances -- stars: evolution -- open clusters and associations: individual: NGC 6475

Offprint request: P. Sestito, sestito@arcetri.astro.it

SIMBAD Objects



© ESO 2003

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.