Coordinated multi-wavelength observations of Sgr A*

Eckart, A.; Schödel, R.; Baganoff, F. K.; Morris, M.; Bertram, T.; Dovciak, M.; Dowries, D.; Duschl, W. J.; Karas, V.; König, S.; Krichbaum, T.; Krips, M.; Kunneriath, D.; Lu, R.-S.; Markoff, S.; Mauerhan, J.; Meyer, L.; Moultaka, J.; Muzic, K.; Najarro, F.; Schuster, K.; Sjouwerman, L.; Straubmeier, C.; Thum, C.; Vogel, S.; Wiesemeyer, H.; Witzel, G.; Zamaninasab, M.; Zensus, A.
"Journal of Physics: Conference Series, Volume 131, Proceedings of "The Universe Under the Microscope - Astrophysics at High Angular Resolution", held 21-25 April 2008, in Bad Honnef, Germany. Editors: Rainer Schoedel, Andreas Eckart, Susanne Pfalzner and Eduardo Ros, pp. 012002 (2008)."


We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the ~4x106Modot super-massive black hole (SMBH) at the Galactic Center. The goal of these coordinated multi-wavelength observations is to investigate the variable emission from Sgr A* in order to obtain a better understanding of the underlying physical processes in the accretion flow/outflow. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescope (July 2005, May 2007) and the ACIS-I instrument aboard the Chandra X-ray Observatory (July 2005). We report on a polarized NIR flare synchronous to a 8x1033 erg/s X-ray flare in July 2005, and a further flare in May 2007 that shows the highest sub-flare to flare contrast observed until now. The observations can be interpreted in the framework of a model involving a temporary disk with a short jet. In the disk component flux density variations can be explained due to hot spots on relativistic orbits around the central SMBH. The variations of the sub-structures of the May 2007 flare are interpreted as a variation of the hot spot structure due to differential rotation within the disk.