The rotation-lithium depletion correlation in the β Pictoris association and the LDB age determination

¹ INAF–Catania Astrophysical Observatory, via S.Sofia, 78 95123 Catania, Italy
e-mail: sergio.messina@oact.inaf.it
² Universitá di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, via S. Sofia 78, 95123 Catania, Italy
³ Department of Physics & Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
⁴ York Creek Observatory, Georgetown, Tasmania, Australia
⁵ INAF–Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁶ Instituto de Astronomía y Física del Espacio (IAFE-CONICET), Buenos Aires, Argentina
⁷ IAU Minor Planet Center code D79, 2 Yandra Street, Vale Park, 5081 South Australia, Australia
⁸ Observatorio Astronómico de Córdoba, Laprida 854, X5000BGR, Córdoba, Argentina
⁹ Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), 1418 Córdoba, Argentina
¹⁰ Harlingten Atacama Observatory, San Pedro de Atacama, Chile
¹¹ Aryabhatta Research Institute of Observational Sciences, Manora Peak, 263129 Nainital, India
¹² Klein Karoo Observatory, Western Cape, South Africa

Received: 16 March 2016
Accepted: 24 July 2016

Abstract

Context. Evidence exists in the 125-Myr Pleiades cluster, and more recently in the 5-Myr NGC 2264 cluster, to show that rotation plays a key role in lithium (Li) depletion processes among low-mass stars. Fast rotators appear to be less Li-depleted than equal-mass slow rotators.

Aims. We intend to explore the existence of a Li depletion-rotation connection among the β Pictoris members at an age of about 24 Myr, and to use this correlation either to confirm or to improve age estimates based on the lithium depletion boundary (LDB) modeling.

Methods. We photometrically monitored all the known members of the β Pictoris association with at least one lithium equivalent width (Li EW) measurement from the literature.

Results. We measured the rotation periods of 30 members for the first time and retrieved the rotation periods for another 36 members from the literature, building a catalogue of 66 members with a measured rotation period and Li EW.

Conclusions. We find that in the 0.3 < M < 0.8M_⊙ range, there is a strong correlation between rotation and Li EW. For higher mass stars, no significant correlation is found. For very low-mass stars in the Li depletion onset, at about 0.1 M_⊙, there are too few data to infer a significant correlation. The observed Li EWs are compared with those predicted by the Dartmouth stellar evolutionary models that incorporate the effects of magnetic fields. After decorrelating the Li EW from the rotation period, we find that the hot side of the LDB is well fitted by Li EW values that correspond to an age of 25 ± 3 Myr, which is in good agreement with independent estimates from the literature.