The Sgr A* stellar cluster: New NIR imaging and spectroscopy

We report preliminary results based on new near-infrared observations of th e central stellar cluster of our Galaxy conducted with the infrared spectro meter ISAAC at the ESO VLT UT1 and the MPE speckle camera SHARP at the ESO NTT. We obtained lambda/Delta lambda greater than or equal to 3000 K-band s pectroscopy of the 2.058 mu m He I, 2.165 mu m Br gamma emission lines, and 2.29 mu m CO bandhead absorption line. These data demonstrate clearly that there is no strong CO bandhead absorption originating in the northern part (S1/S2 area) of the central stellar cluster at the position of Sgr A*. Thi s makes it likely that these K similar to 14.5 stars are O9 - B0.5 stars wi th masses of 15 to 20 M.. Weaker CO bandhead absorption in the southern par r of the cluster (S10/S11 area) could be due to contributions from neighbou ring stars. We also report the detection of Br gamma line emission at the p osition of the central stellar cluster which could be associated with the ' mini-spiral' rather than with the Sgr A* cluster itself. At the NTT we obta ined another epoch epoch of proper motion measurements. The changes of sour ce positions are consistent with the proper motion velocities derived from earlier epochs.