IC 2602: a lithium depletion boundary age and new candidate low-mass stellar members

Abstract

We report the results from a photometric and spectroscopic survey of ∼1.4 deg² of the young open cluster IC 2602. Fourteen objects have been identified as having magnitudes, spectral types and radial velocities consistent with being probable or possible low-mass stellar members of the cluster. We have used the observed location of the lithium depletion boundary in the sequence defined by these objects to place a new and improved constraint on the cluster age, τ= 46⁺⁶_-5 Myr. This new determination is larger by a factor ∼1.3-1.8 than the majority of age estimates which have been obtained using the main-sequence turn-off or pre-main-sequence isochrone techniques. It is thus consistent with the trend indicated by the results of similar studies on other young open clusters. Based on this new age, we set a lower limit on the cluster mass function over the range M = 0.054 - 0.24 M_⊙, dn/dM > 46 M^-1_⊙. If the mass function of IC 2602 has a form similar to that of other young clusters and associations then future wide, deep surveys can expect to unearth at least a handful of brown dwarfs which could potentially serve as benchmark objects. Based on observations made with Anglo-Australian Telescope at Siding Spring Observatory, Australia.