Publication: Gaia-ESO Survey: Role of magnetic activity and starspots on pre-main-sequence lithium evolution
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2022-03-10
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Abstract
Context. It is now well-known that pre-main-sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. Aims. We tested a new set of pre-main-sequence models that include radius inflation due to the presence of starspots or to magnetic inhibition of convection. We used five clusters observed by the Gaia-ESO Survey that span the age range similar to 10-100 Myr, in which these effects could be important. Methods. The Gaia-ESO Survey radial velocities were combined with astrometry from Gaia EDR3 to obtain clean lists of high-probability members for the five clusters. A Bayesian maximum likelihood method was adopted to fit the observed cluster sequences to theoretical predictions to derive the best model parameters and the cluster reddening and age. Models were calculated with different values of the mixing length parameter (alpha(ML) = 2.0, 1.5 and 1.0) for the cases without spots or with effective spot coverage beta(spot) = 0.2 and 0.4. The models were also compared with the observed lithium depletion patterns. Results. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori, both a reduced convection efficiency, with alpha(ML) = 1.0, and an effective surface spot coverage of about 20% are required. We obtained ages of 18(-4.0)(+1.5) - Myr and 21(-3.0)(+3.5)Myr for Gamma Vel A and B, respectively, and 19(-7.0)(+1.5) 19(-7.0+)(1.5) Myr for 25 Ori. However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451 B at 30(-5.0)(3.0) Myr, NGC 2547 at 35(-4.0)(+4.0) Myr, and NGC 2516 at 138(-42)(+48) Myr) are consistent with standard models (i.e. alpha(ML) = 2.0 and no spots) except at low masses: a 20% spot coverage appears to reproduce the sequence of M-type stars better and might explain the observed spread in lithium abundances. Conclusions. The quality of Gaia-ESO data combined with Gaia allows us to gain important insights on pre-main-sequence evolution. Models including starspots can provide a consistent explanation of the cluster sequences and lithium abundances observed in young clusters, although a range of starspot coverage is required to fully reproduce the data.
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© ESO 2022. Artículo firmado por 27 autores. We thank E. Martín for his fruitful comments as referee of this paper. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes 188.B-3002, 193.B-0936, and 197.B-1074. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council. This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012". The results presented here benefit from discussions held during the Gaia ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. We acknowledge the support from INAF in the form of the grant for mainstream projects "Enhancing the legacy of the Gaia-ESO Survey for open clusters science". E.T. acknowledges Czech Science Foundation GAC. R (Project: 21-16583M) and the "visiting fellow program" of the University of Pisa. P.G.P.M. and S.D. acknowledge INFN (Iniziativa specifica TAsP). E.P. and N.S. acknowledge financial support from Progetto Main Stream INAF "Chemo-dynamics of globular clusters: the Gaia revolution". R.B. acknowledges financial support from the project PRININAF 2019 "Spectroscopically Tracing the Disk Dispersal Evolution". F.J.E. acknowledges financial support from the Spanish MINECO/FEDER through the grant AYA2017-84089 and MDM-2017-0737 at Centro de Astrobiología (CSIC-INTA), Unidad de Excelencia María de Maeztu, and from the European Union's Horizon 2020 research and innovation programme under Grant Agreement no. 824064 through the ESCAPE -The European Science Cluster of Astronomy & Particle Physics ESFRI Research Infrastructures project. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research made use of astropy (http://www.astropy.org), a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018).