Variable and Polarised Near-infrared Emission from the Galactic Centre
Résumé
Infrared observations of the Galactic Centre (GC) provide a unique opportunity to study stellar and bow-shock polarisation effects in a dusty environment. For the infrared counterpart of the supermassive black hole Sgr A* these observations reveal new insights into the physical processes at work. The observations were carried out with NACO in the Ks-band (2.2 µm) from 2004 to 2012 and several linearly polarised flares were observed during these years. We find that the distribution of polarised flux density is closely related to the single-state power-law distribution of the total flux densities. A typical polarisation degree of the order of 10-20% and a preferred polarisation angle of 13° ± 15° are derived, likely linked to the intrinsic orientation of the Sgr A* system. We discuss different scenarios for the accretion process for the Sgr A* system based on our findings.