The evolution of lithium in FGK dwarf stars The lithium-rotation connection and the Li desert

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We investigate two topics regarding solar mass FGK-type stars, the lithium-rotation connection (LRC), and the existence of the 'lithium desert'. We determine the minimum critical rotation velocity (v sin i), related with the LRC separating slow from rapid stellar rotators, to be 5 km s(-1). This value also splits different stellar properties. For the first time we explore the behaviour of the LRC for some stellar associations with ages between 45 Myr and 120 Myr. This allows us to study the LRC age dependence at the beginning of the general spin-down stage for low-mass stars, which starts at similar to 30-40 Myr. We find that each stellar group presents a characteristic minimum lithium depletion connected to a specific high rotation velocity and that this minimum changes with age. For instance, the minimum changes from similar to 50 km s(-1) to less than 20 km s(-1) in 200 Myr. This desert was described as a limited region in the A(Li)-T-eff map containing no stars. Using T-eff from Gaia DR2 we detect 30 stars inside and/or near the same box originally defined as the lithium desert. Due to their intrinsic T-eff errors some of these stars may be inside or outside the box, implying to a high probability that the box contains several stars. This leads us to consider that the lithium desert appears to be more a statistical distribution fluctuation than a real problem. We conclude that the lithium desert is rather due to a statistical distribution fluctuation than a real physical problem.
© ESO 2021. The authors thank the anonymous referee for the constructive comments and helpful insights. This work has made use of SVODiscTool, developed by the Spanish Virtual Observatory (Centro de Astrobiología (CSIC-INTA), Unidad de Excelencia María de Maeztu), a project supported by the Spanish State Research Agency (AEI) through grants AyA2017-84089 and MDM-2017-0737. C.CH acknowledges support from SECYT/UNC and CONICET. 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. Authors also thank to Leo Girardi for providing the PARAM code. 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. SRF acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grant number AYA2016-75808-R, AYA2017-90589-REDT and S2018/NMT-429, and from the CAM-UCM under grant number PR65/19-22462 and from the CAM-UCM under grant number PR65/19-22462. CC acknowledges financial support from the Spanish Ministry of Science and Innovation through grants AYA2016-79425-C3-1/2/3-P and BES-2017-080769.
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