High resolution visual and IR images of the embedded young cluster associated with the molecular cloud and "blister" H II region GM24 are presented. The cluster contains more than 23 stars, most of them showing large IR excesses at λ ≥ 2.2 μm. The distance to the complex is d = 2.0 kpc and the total luminosity is Ltot ≅ 1.5x105Lsun.

We have measured the He I D3 line 5876 Å, in 32 F-type young open cluster stars and in 4 field stars. Combining our results with previous observations of D3 we strengthen the following conclusions: (a) Sub-surface convective zones appear, on the main sequence, around F0 (B - V 0.3). (b) The stars between F0 nd F5 (0.3 B - V 0.42) are

Not Available

Not Available

Not Available

Not Available