On the evolutionary status of the LMC cluster NGC 2004.

Abstract

IUE observations of hot stars in the LMC young cluster NGC 2004 have been used to derive effective temperatures and bolometric luminosities well below the turn-off. No star is found close to the upper main sequence. Massive stars appear arranged on a vertical sequence at temperatures much lower than those of the ZAMS. Among the fainter objects, three lie on the ZAMS, and some may be in a pre-MS phase. The presence of red giants at luminosities much lower than that of the evolved blue giants, together with stars still approaching the main sequence, suggests a star formation process much more continuous in time than generally suspected.