The <i>Gaia</i>-ESO survey: a lithium depletion boundary age for NGC 2232
A. S. Binks, R. D. Jeffries, R. J. Jackson, E. Franciosini, G. G. Sacco, A. Bayo, L. Magrini, S. Randich, J. Arancibia-Silva, M. Bergemann, A. Bragaglia, G. Gilmore, A. Gonneau, A. Hourihane, P. Jofré, A. J. Korn, L. Morbidelli, L. Prisinzano, C. C. Worley, S. Zaggia
Abstract
ABSTRACT Astrometry and photometry from Gaia and spectroscopic data from the Gaia-ESO Survey (GES) are used to identify the lithium depletion boundary (LDB) in the young cluster NGC 2232. A specialized spectral line analysis procedure was used to recover the signature of undepleted lithium in very low luminosity cluster members. An age of 38 ± 3 Myr is inferred by comparing the LDB location in absolute colour−magnitude diagrams (CMDs) with the predictions of standard models. This is more than twice the age derived from fitting isochrones to low-mass stars in the CMD with the same models. Much closer agreement between LDB and CMD ages is obtained from models that incorporate magnetically suppressed convection or flux-blocking by dark, magnetic starspots. The best agreement is found at ages of 45−50 Myr for models with high levels of magnetic activity and starspot coverage fractions &gt;50 per cent, although a uniformly high spot coverage does not match the CMD well across the full luminosity range considered.