SIMBAD references

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.