Abstract
High angular resolution and high sensitivity observations at wavelengths of 1.3 and 3.6 cm have detected three new ultracompact emission regions in the core of the W51 (regions d and e). In total, five ultracompact continuum objects of diameter <300 to 3000 AU are located in this region. These sources may best be explained as photoionized stellar winds. This suggests that there may exist a quasi stable point in early stellar evolution where observable HII regions are formed by stellar winds around massive stars.The J,K=(9,8) NH, maser associated with W51 d has been shown to have a minimum brightness temperature of 2.7 106 K. This maser is most probably saturated.
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