Detection of the Sgr A* activity at 3.8 and 4.8 mum with NACO

Yann Clénet (1, 2, 3) , Daniel Rouan (2, 3) , Damien Gratadour (2, 3) , François Lacombe (2, 3) , Éric Gendron (2, 3) , Reinhard Genzel (4) , Thomas Ott (4) , Rainer Schödel (5) , Pierre Léna (2, 3)

1 ESO - European Southern Observatory
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 Pôle Astronomie du LESIA
4 MPE - Max-Planck-Institut für Extraterrestriche Physik
5 Physikalisches Institut, Universität zu Köln

L'-band (lambda= 3.8 mum) and M'-band (lambda= 4.8 mum) observations of the Galactic Center region, performed in 2003 at VLT (ESO) with the adaptive optics imager NACO, have lead to the detection of an infrared counterpart of the radio source Sgr A* at both wavelengths. The measured fluxes confirm that the Sgr A* infrared spectrum is dominated by the synchrotron emission of nonthermal electrons. The infrared counterpart exhibits no significant short term variability but demonstrates flux variations on daily and yearly scales. The observed emission arises away from the position of the dynamical center of the S2 orbit and would then not originate from the closest regions of the black hole.

Domaines: Astrophysique [astro-ph]

Yann Clénet, Daniel Rouan, Damien Gratadour, François Lacombe, Éric Gendron, et al.. Detection of the Sgr A* activity at 3.8 and 4.8 mum with NACO. Astronomy and Astrophysics - A&A, 2004, 424, pp.L21-L25. ⟨10.1051/0004-6361:200400045⟩. ⟨hal-03785837⟩