The lithium depletion boundary in NGC 2547 as a test of pre-main-sequence evolutionary models

Intermediate resolution spectroscopy from the European Southern Observatory Very Large Telescope is analysed for 63 photometrically selected low-mass (0.08- 0.30 M-circle dot) candidates of the open cluster NGC 2547. We have confirmed membership for most of these stars using radial velocities, and found that lithium remains undepleted for cluster stars with I > 17.54 +/- 0.14 and K-s > 14.86 +/- 0.12. From these results, several pre-main-sequence evolutionary models give almost model independent ages of 34-36 Myr, with a precision of 10 per cent. These ages are only slightly larger than the ages of 25-35(+/- 5) Myr obtained using the same models to fit isochrones to higher mass stars descending towards the zero-age main-sequence, both in empirically calibrated and theoretical colour-magnitude diagrams. This agreement between age determinations in different mass ranges is an excellent test of the current generation of low-mass pre-main-sequence stellar models and lends confidence to ages determined with either method between 30 and 120 Myr.