Lithium depletion boundary, stellar associations, and Gaia^⋆

¹ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 San Antonio, Breña Baja, Santa Cruz de Tenerife, Spain
e-mail: pgalindo@hotmail.cl
² Centro de Estudios de Física del Cosmos de Aragón (CEFCA), Plaza San Juan 1, 44001 Teruel, Spain
e-mail: pgalindo@cefca.es
³ Departamento de Astrofísica, Centro de Astrobiología (CAB, CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁴ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
⁵ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
⁶ Universidad de La Laguna, Dpto. Astrofísica, 38206 La Laguna, Tenerife, Spain
⁷ Inst. Física y Astronomía, Fac. Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Valparaíso, Chile
⁸ Núcleo Milenio Formación Planetaria – NPF, Valparaíso, Chile
⁹ European Organisation for Astronomical Research in the Southern Hemisphere (ESO), Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
¹⁰ Departamento de Inteligencia Artificial, UNED, Juan del Rosal 16, 28040 Madrid, Spain
¹¹ Observatorio Astronómico Nacional (OAN-IGN) – Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
¹² Fundación Galileo Galilei – INAF, Rambla José Ana Fernández Pérez 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain
¹³ Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA

Received: 18 April 2021
Accepted: 12 April 2022

Abstract

Context. Stellar ages are key to improving our understanding of different astrophysical phenomena. However, many techniques to estimate stellar ages are highly model-dependent. The lithium depletion boundary (LDB), based on the presence or absence of lithium in low-mass stars, can be used to derive ages in stellar associations of between 20 and 500 Ma.

Aims. The purpose of this work is to revise former LDB ages in stellar associations in a consistent way, taking advantage of the homogeneous Gaia parallaxes as well as bolometric luminosity estimations that do not rely on monochromatic bolometric corrections.

Methods. We studied nine open clusters and three moving groups characterised by a previous determination of the LDB age. We gathered all the available information from our data and the literature: membership, distances, photometric data, reddening, metallicity, and surface gravity. We re-assigned membership and calculated bolometric luminosities and effective temperatures using distances derived from Gaia DR2 and multi-wavelength photometry for individual objects around the former LDB. We located the LDB using a homogeneous method for all the stellar associations. Finally, we estimated the age by comparing it with different evolutionary models.

Results. We located the LDB for the twelve stellar associations and derived their ages using several theoretical evolutionary models. We compared the LDB ages among them, along with data obtained with other techniques, such as isochrone fitting, ultimately finding some discrepancies among the various approaches. Finally, we remark that the 32 Ori MG is likely to be composed of at least two populations of different ages.