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Paper text:
the advent of high - quality near - infrared instrumentation has opened up a new window on the birth sites of massive stars .
the formation time scales of a massive star is short , of the order of 100,000 years .
this means that the newly born stars are still deeply embedded in their parental molecular cloud .
not much is known about the onset of the stellar wind or the initial rotation properties of young massive stars .
occurring behind large amounts of extinction , inside their natal molecular cloud , these evolutionary stages can only be observed at near - infrared wavelengths .
we have identified 38 ob type stars inside massive star forming regions ( @xcite ) using k - band spectroscopy .
they are classified based on the classification scheme of @xcite .
three o3-o4 stars are detected , while only a few o3 stars are known in our galaxy .
the k - band spectra of the ob stars are in general similar to those of the ( more evolved ) ob stars located in ob associations and the field .
this suggest that the k - band spectral properties of the very young ob stars are already indistinguishable from those of the more evolved stars .
profile of 4 young o5-o6 v stars in comparison with a br@xmath0  profile of a o5v field star ( lower spectrum , right panel).,width=415 ]    a few stars classified as early o stars ( o5-o6v ) show a peculiar behaviour of the br@xmath0  line ( fig .
[ fig : brg ] ) ; the line is either not present , in emission , or the profile is partly filled in .
this might be caused by an enhanced mass - loss .
however , this would only happen if the stellar mass - loss is as high as that of supergiants ( @xcite , lenorzer et al , these proceedings ) . veiling by dust or free - free emission is unlikely as the intrinsically weak lines like civ and niii are detected .
contrary to the suggestion found in our data that the young stars possess a relatively strong wind , evidence has been presented for a class of young ob stars which have unusually weak winds for their spectral type ( @xcite , @xcite ) .    to distinguish between these two scenarios for the stellar wind of the youngest ob stars , a careful analysis of spectral lines sensitive to the wind density is needed .
the br@xmath0  line in the k - band is not the best line for this analysis .
br@xmath1  in the l - band is more sensitive to the stellar wind density ( @xcite ) .
currently a observing program to obtain high resolution spectra of the br@xmath1  line with isaac on the vlt is underway .
we have obtained high resolution ( r = 10,000 ) k - band spectra of candidate young massive stars deeply embedded in high - mass star - forming regions . 
 these objects were selected from a near - infrared survey of 44 regions of high - mass star - formation ( @xcite ) . in these clusters , 
 38 ob stars are identified whose k - band spectra are dominated by photospheric emission . in almost all those stars , 
 the k - band spectra are indistinguishable from field stars . however , in some stars the profile of the br@xmath0 line is different ( less deep , or absent ) from those of the o field stars . 
 one of the explanations of these profiles might be an enhanced mass - loss .