Revealing the Chamaeleon: First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis

Abstract

We have identified several lithium-rich low-mass (0.08<M<0.3 Msun). stars within 5.5 deg of the young open cluster Eta Chamaeleontis, nearly four times the radius of previous search efforts. We propose 4 new probable cluster members and 3 possible members requiring further investigation. Candidates were selected on the basis of DENIS and 2MASS photometry, NOMAD astrometry and extensive follow-up spectroscopy. Several of these stars show substantial variation in their H-alpha emission line strengths on timescales of days to months, with at least one event attributable to accretion from a circumstellar disk. These findings are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an abnormally top-heavy Initial Mass Function, as proposed by some authors.

arXiv comment7 pages. To appear in the proceedings of the 16th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun (Seattle WA, 29 Aug-2 Sep 2010). High quality figures available in the references therein