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Centro de Astrofísica da Universidade do Porto

The Gaia-ESO Survey: chemical signatures of rocky accretion in a young solar-type star

L. Spina, F. Palla, S. Randich, G. G. Sacco, R. D. Jeffries, L. Magrini, E. Franciosini, M. R. Meyer, G. Tautvai¨ienė, G. Gilmore, E. J. Alfaro, C. A. Prieto, T. Bensby, A. Bragaglia, E. Flaccomio, S. Koposov, A. C. Lanzafame, M. T. Costado, A. Hourihane, C. Lardo, J. Lewis, L. Monaco, L. Morbidelli, S. G. Sousa, C. Worley, S. Zaggia

Abstract
It is well known that newly formed planetary systems undergo processes of orbital reconfiguration and planetary migration. As a result, planets or protoplanetary objects may accrete onto the central star, being fused and mixed into its external layers. If the accreted mass is sufficiently high and the star has a sufficiently thin convective envelope, such events may result in a modification of the chemical composition of the stellar photosphere in an observable way, enhancing it with elements that were abundant in the accreted mass. The recent Gaia-ESO Survey observations of the 1020 Myr old Gamma Velorum cluster have enabled identifying a star that is significantly enriched in iron with respect to other cluster members. In this Letter we further investigate the abundance pattern of this star, showing that its abundance anomaly is not limited to iron, but is also present in the refractory elements, whose overabundances are correlated with the condensation temperature. This finding strongly supports the hypothesis of a recent accretion of rocky material.

Keywords
stars: abundances – stars: chemically peculiar – stars: pre-main sequence – galaxies: star clusters: individual: Gamma Velorum – planet-star interactions – techniques: spectroscopic

Astronomy and Astrophysics
Volume 582, Page L6
October 2015

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