2007MNRAS.375..764T

In this article we summarize and discuss the infrared, radio and X-ray emission from the supermassive black hole in the Galactic Centre, SgrA*. We include new results from near-infrared polarimetric imaging observations obtained on 2006 May 31. In that night, a strong flare in K_sband (2.08 µm) reaching top fluxes of ∼16 mJy could be observed. This flare was highly polarized (up to ∼40 per cent) and showed clear substructure on a time-scale of 15 min, including a swing in the polarization angle of about 70°. For the first time we were able to observe both polarized flux and short-time variability, with high significance in the same flare event. This result adds decisive information to the puzzle of the SgrA* activity. The observed polarization angle during the flare peak is the same as observed in two events in 2004 and 2005. Our observations strongly support the dynamical emission model of a decaying plasma hotspot orbiting SgrA* on a relativistic orbit. The observed polarization parameters and their variability with time might allow to constrain the orientation of accretion disc and spin axis with respect to the Galaxy.