Abstract

On the formation of massive stars

Lex Kaper (Astronomical Institute Univ. Amsterdam)

L.E. Ellerbroek (Amsterdam), B.B. Ochsendorf (Amsterdam), A. Bik (MPIA Heidelberg)

The birth process and (early) evolution of massive stars is still poorly understood. Massive stars are rare, their birthplaces are hidden from view and their formation timescale is short. So far, our physical knowledge of these young massive stars has been derived from near-IR imaging and spectroscopy, revealing populations of young OB-type stars, some still surrounded by a (remnant?) accretion disk, others apparently ``normal'' main sequence stars powering H II regions. The most important spectral features of OB-type stars are, however, located in the UV and optical range. With VLT/X-shooter it is possible to extend the spectral coverage of these young massive stars into the optical range, to better determine their photospheric properties, to search for signs of active accretion, and to characterize the physical structure of the circumstellar disk. We present the first results of our program to obtain spectra of deeply embedded, young massive stars, with X-shooter, the most powerful spectrograph in the world.