Variations in the spectral slope of sagittarius A* during a near-infrared flare

S. Gillessen, F. Eisenhauer, E. Quataert, R. Genzel, T. Paumard, S. Trippe, T. Ott, R. Abuter, A. Eckart, P. O. Lagage, M. D. Lehnert, L. J. Tacconi, F. Martins

Research output: Contribution to journalArticlepeer-review

88 Scopus citations


We have observed a bright flare of Sgr A* in the near-infrared with the adaptive optics-assisted integral-field spectrometer SINFONI. Within the uncertainties, the observed spectrum is featureless and can be described by a power law. Our data suggest that the spectral index is correlated with the instantaneous flux and that both quantities experience significant changes within less than 1 hour. We argue that the near-infrared flares from Sgr A* are due to synchrotron emission of transiently heated electrons, the emission being affected by orbital dynamics and synchrotron cooling, both acting on timescales of ≈20 minutes.

Original languageEnglish (US)
Pages (from-to)L163-L166
JournalAstrophysical Journal
Issue number2 II
StatePublished - Apr 1 2006
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Black hole physics
  • Galaxy: center
  • Infrared: stars
  • Techniques: spectroscopic


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