The Gaia-ESO Survey: the first abundance determination of the pre-main-sequence cluster gamma Velorum
L. Spina, S. Randich, F. Palla, G. G. Sacco, L. Magrini, E. Franciosini, L. Morbidelli, L. Prisinzano, E. J. Alfaro, K. Biazzo, A. Frasca, J. I. González Hernández, S. G. Sousa, V. Zh. Adibekyan, E. Delgado Mena, D. Montes, H. M. Tabernero, A. Klutsch, G. Gilmore, S. Feltzing, R. D. Jeffries, G. Micela, A. Vallenari, T. Bensby, A. Bragaglia, E. Flaccomio, S. Koposov, A. C. Lanzafame, E. Pancino, A. Recio-Blanco, R. Smiljanic, M. T. Costado, F. Damiani, V. Hill, A. Hourihane, P. Jofré, P. de Laverny, T. Masseron, C. Worley
Aims. In this context, we present the analysis of the metallicity of the gamma Velorum cluster, based on the products distributed in the first internal release of the Gaia-ESO Survey.
Methods. The gamma Velorum candidate members have been observed with FLAMES, using both UVES and Giraffe, depending on the target brightness and spectral type. In order to derive a solid metallicity determination for the cluster, membership of the observed stars must be first assessed. To this aim, we use several membership criteria including radial velocities, surface gravity estimates, and the detection of the photospheric lithium line.
Results. Out of the 80 targets observed with UVES, we identify 14 high-probability members. We find that the metallicity of the cluster is slightly subsolar, with a mean [ Fe/H ] = −0.057 ± 0.018 dex. Although J08095427-4721419 is one of the high-probability members, its metallicity is significantly larger than the cluster average. We speculate about its origin as the result of recent accretion episodes of rocky bodies of ~60 M⊕ hydrogen-depleted material from the circumstellar disk.
Astronomy and Astrophysics