%0 Journal Article
%T Flares and variability from Sagittarius A*: five nights of simultaneous multi-wavelength observations
%A X. Haubois
%A K. Dodds-Eden
%A A. Weiss
%A T. Paumard
%A G. Perrin
%A Y. Cl¨Śnet
%A S. Gillessen
%A P. Kervella
%A F. Eisenhauer
%A R. Genzel
%A D. Rouan
%J Physics
%D 2013
%I arXiv
%R 10.1051/0004-6361/201117725
%X Aims. We report on simultaneous observations and modeling of mid-infrared (MIR), near-infrared (NIR), and submillimeter (submm) emission of the source Sgr A* associated with the supermassive black hole at the center of our Galaxy. Our goal was to monitor the activity of Sgr A* at different wavelengths in order to constrain the emitting processes and gain insight into the nature of the close environment of Sgr A*. Methods. We used the MIR instrument VISIR in the BURST imaging mode, the adaptive optics assisted NIR camera NACO, and the sub-mm antenna APEX to monitor Sgr A* over several nights in July 2007. Results. The observations reveal remarkable variability in the NIR and sub-mm during the five nights of observation. No source was detected in the MIR, but we derived the lowest upper limit for a flare at 8.59 microns (22.4 mJy with A_8.59mu = 1.6+/- 0.5). This observational constraint makes us discard the observed NIR emission as coming from a thermal component emitting at sub-mm frequencies. Moreover, comparison of the sub-mm and NIR variability shows that the highest NIR fluxes (flares) are coincident with the lowest sub-mm levels of our five-night campaign involving three flares. We explain this behavior by a loss of electrons to the system and/or by a decrease in the magnetic field, as might conceivably occur in scenarios involving fast outflows and/or magnetic reconnection.
%U http://arxiv.org/abs/1301.4644v1