Spectroscopy
Eckart et al (1999) reported results based on new NIR observations of the central stellar cluster of our Galaxy conducted with the infrared spectrometer ISAAC at the ESO VLT UT1 and the MPE speckle camera SHARP at the ESO NTT (see also Herbst et al 1993, Figer et al 2000). The ISAAC observations resulted in λ/Δλ∼ 5000 K-band spectra of the 2.058 μm He I, 2.165 μm Br γ emission lines, and 2.29 μm CO bandhead absorption line. These data clearly demonstrate 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^∗. This makes it likely that these K ∼ 14.5 stars are O9–B0.5 stars with masses of 15 to 20 M_ּ. Weaker CO-bandhead absorption in the southern part of the cluster (S10/S11 area) is most likely due to contributions from neighbouring stars. Eckart et al (1999) also report the detection of Br γ line emission at the position of the central stellar cluster which could be associated with the ‘mini spiral’ rather than with the Sgr A^∗ cluster itself.