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Issue A&A
Volume 424, Number 2, September III 2004
Page(s) L21 - L25
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:200400045



A&A 424, L21-L25 (2004)
DOI: 10.1051/0004-6361:200400045

Letter

Detection of the Sgr A* activity at 3.8 and 4.8 $\mathsf{\mu}$m with NACO

Y. Clénet1, D. Rouan2, D. Gratadour2, F. Lacombe2, E. Gendron2, R. Genzel3, T. Ott3, R. Schödel4 and P. Léna2

1  European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
    e-mail: yclenet@eso.org
2  Observatoire de Paris, LESIA, 5 place Jules Janssen, 92195 Paris Cedex, France
    e-mail: [daniel.rouan; damien.gratadour; francois.lacombe; eric.gendron; pierre.lena]@obspm.fr
3  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching bei München, Germany
    e-mail: [genzel; ott]@mpe.mpg.de
4  I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937, Köln, Germany
    e-mail: rainer@ph1.uni-koeln.de

(Received 27 April 2004 / Accepted 25 July 2004 )

Abstract
L'-band ( $\lambda=$ 3.8  $\mu$m) and M'-band ( $\lambda=$ 4.8  $\mu$m) 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.


Key words: Galaxy: center -- infrared: stars -- instrumentation: adaptive optics

SIMBAD Objects



© ESO 2004


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