Adaptive optics L-band observations of the galactic center region

L-band adaptive optics observations of the Galactic Center region have been performed in June 1999 and May 2000 at La Silla with the 3.6 m telescope, using the ADONIS adaptive optics system. In June 1999, we used a dedicated infrared wave-front sensor, RASOIR. This paper reports on the photometry and astrometry of more than 40 stars. Thanks to additional adaptive optics K-band observations made at CFHT, colour-magnitude diagrams have been constructed to identify individual sources with various types of stars known in this region (AGB, LPV, WC9, WN9/WN10, Ofpe/WN9, YSO). The so-called "cool slash" stars (Ofpe/WN9) appear to be numerous in the field and an estimation of the extinction coefficient towards the Galactic Center from the colours of these intrinsically weakly absorbed stars leads to A(K) = 2.7, which is among the lowest published values.