We consider the effect of uncertainties in solar models on the p-mode frequencies of moderate degree (40 l 100). This is done by means of an asymptotic relation that provides a simple way of estimating differences in p-mode frequencies of two solar models. Also, we have investigated the possibility for separating different contributions to the

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

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