The bi-modal Li-7 distribution of the Milky Way's thin-disk dwarf stars The role of Galactic-scale events and stellar evolution

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Context. The lithium abundance, A(Li), in stellar atmospheres suffers from various enhancement and depletion processes during the star's lifetime. While several studies have demonstrated that these processes are linked to the physics of stellar formation and evolution, the role that Galactic-scale events play in the galactic A(Li) evolution is not yet well understood. Aims. We aim to demonstrate that the observed A(Li) bi-modal distribution, in particular in the FGK-dwarf population, is not a statistical artefact and that the two populations connect through a region with a low number of stars. We also want to investigate the role that Galactic-scale events play in shaping the A(Li) distribution of stars in the thin disk. Methods. We use statistical techniques along with a Galactic chemical evolution model for A(Li) that includes most of the well-known Li-7 production and depletion channels. Results. We confirm that the FGK main-sequence stars belonging to the Milky Way's thin disk present a bi-modal A(Li) distribution. We demonstrate that this bi-modality can be generated by a particular Milky Way star formation history profile combined with the stellar evolution's Li-7 depletion mechanisms. We show that A(Li) evolution can be used as an additional proxy for the star formation history of our Galaxy.
We thank the anonymous reviewer for his/her comments and suggestions that helped us improve this manuscript. SFR acknowledges support from a Spanish postdoctoral fellowship `Ayudas para la atracción del talento investigador. Modalidad 2: jóvenes investigadores, financiadas por la Comunidad de Madrid' under grant number 2017-T2/TIC-5592. His work has been supported by the Madrid Government (Comunidad de Madrid-Spain) under the Multiannual Agreement with Complutense University in the line Program to Stimulate Research for Young Doctors in the context of the V PRICIT (Regional Programme of Research and Technological Innovation). SRF and CC acknowledge financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2016-75808-R, AYA2017-90589REDT, YA2016-79425-C3-2-P, and S2018/NMT-429, and from the CAM-UCM under grant number PR65/19-22462. FLA and R de la R. acknowledge support from the Faculty of the European Space Astronomy Centre (ESAC) Funding references 569 and 570, respectively. FLA would like to thank the technical support provided by A. Parras (CAB), Dr. J. A. Prieto (UCLM) and MSc J. Gómez-Malagón. This research has made use of the Spanish Virtual Observatory ( supported from the Spanish MICINN/FEDER through grant AyA2017-84089. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.
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