First simultaneous NIR/X-ray detection of a flare from Sgr A

By A. Eckart, F. Baganoff, Mark R. Morris, M. Bautz, W. N. Brandt, G. Garmire, R. Genzel, T. Ott, G. Ricker, C. Straubmeier and 4 more. 2004

153 citations recorded by the source corpus.

We report on the first simultaneous near-infrared/X-ray detection of the Sgr A* counterpart associated with the massive 3-4 × 10 6 Mblack hole at the center of the Milky Way. The observations have been carried out using the NACO adaptive optics (AO) instrument at the European Southern Observatory's Very Large Telescopeand the ACIS-I instrument aboard the Chandra X-ray Observatory. We also report on quasi-simultaneous observations at a wavelength of 3.4 mm using the Berkeley-Illinois-Maryland Association (BIMA) array. A flare was detected in the X-domain with an excess 2-8 keV luminosity of about 6 × 10 33 erg/s. A fading flare of Sgr A* with >2 times the interim-quiescent flux was also detected at the beginning of the NIR observations, that overlapped with the fading part of the X-ray flare. Compared to 8-9 h before the NIR/X-ray flare we detected a marginally significant increase in the millimeter flux density of Sgr A* during measurements about 7-9 h afterwards. We find that the flaring state can be conveniently explained with a synchrotron self-Compton model involving up-scattered sub-millimeter photons from a compact source component, possibly with modest bulk relativistic motion. The size of that component is assumed to be of the order of a few times the Schwarzschild radius. The overall spectral indices αNIR/X−ray (S ν ∝ ν −α ) of both states are quite comparable with a value of ∼1.3. Since the interim-quiescent X-ray emission is spatially extended, the spectral index for the interim-quiescent state is probably only a lower limit for the compact source Sgr A*. A conservative estimate of the upper limit of the time lag between the ends of the NIR and X-ray flare is of the order of 15 min.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/a6ce8c45f616c9c599897042fa875d3d8939ff89

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In Astronomy and Astrophysics

1. T. Johannsen
2. Ramesh Narayan
3. T. Alexander
4. R. Genzel
5. F. Yuan
6. A. Eckart
7. T. Ott
8. Abraham Loeb

Citations in the corpus

• Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma (2006, background): “Recent multi-wavelength observations of Sgr A* show that near-IR flare activity is central to the activity in X-ray and sub-mm wavelengths (e.g., Eckart et al. 2004, 2006; Gillessen et al. 2006; Yusef-Zadeh et al. 2006).”
• Imaging bright-spots in the accretion flow near the black hole horizon of Sgr A* (2005, methodology): “…and X-ray bands revealed flaring activity on short time-scales (Baganoff et al. 2001; Genzel et al. 2003; Goldwurm et al. 2003; Porquet et al. 2003; Aschenbach et al. 2004; Eckart et al. 2004; Ghez et al. 2004), indicating strong inhomogeneities in the emission close to the black hole horizon.”
• SINFONI in the Galactic Center: Young Stars and Infrared Flares in the Central Light-Month (2005, background): “The key for determining the emission processes is the measurement of the spectral slope and polarization of the variable infrared emission and the simultaneous observations of infrared and X-ray flares (Baganoff et al. 2001; Porquet et al. 2003; Goldwurm et al. 2003; Eckart et al. 2004).”
• DETECTING FLARING STRUCTURES IN SAGITTARIUS A* WITH HIGH-FREQUENCY VLBI (2008, background): “Our description of the hot spot is completed by the spectral index of the power-law distribution of electrons, αspot = 1.3, taken from observations of NIR flares (Eckart et al. 2004).”
• Hot Accretion Flows Around Black Holes (2014, background): “2009), synchrotron self-Compton, or inverse Compton of external radiation (Markoff et al. 2001; Eckart et al. 2004, 2006; Yusef-Zadeh et al. 2009).”
• Imaging optically-thin hotspots near the black hole horizon of Sgr A* at radio and near-infrared wavelengths (2005, background): “However, observations of near-infrared (NIR) and X-ray flaring of Sgr A∗ have implied that the inner regions of the accretion flow are non-uniform (Baganoff et al. 2001; Genzel et al. 2003; Goldwurm et al. 2003; Eckart et al. 2004; Ghez et al. 2004).”
• Polarimetry of near-infrared flares from Sagittarius A* (2006, background): “…combined with theory indicate that the MBH source SgrA* is strongly variable with a NIR/X-ray spectrum involving Synchrotron self-Compton models (Eckart et al. 2004, 2006) and rapid cooling of transiently heated electrons, Doppler beaming, and modulation due to special relativistic aberrations…”
• Black Hole Flares: Ejection of Accreted Magnetic Flux through 3D Plasmoid-mediated Reconnection (2021, background): “…the black hole in the Galactic Center, Sgr A*, shows intriguing infrared and X-ray flares on similarly short dynamical timescales (Baganoff et al. 2001; Eckart et al. 2004; Neilsen et al. 2015) originating from near the horizon (Gravity Collaboration et al. 2018; Collaboration et al. 2021).”
• First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer (2017, background): “On top of this quasi-steady component there is variable emission in the X-ray and infrared bands, which appears as flares, typically a few times per day and lasting for about 1 − 2 h (Bagano ff et al. 2001; Genzel et al. 2003; Eckart et al. 2004; Eisenhauer et al. 2005).”
• GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “…of the flares and the lack of evidence of any standard thin accretion disk emission (Shakura & Sunyaev 1973), a magnetic origin of the flares has been suggested, either from synchrotron or synchrotron-self Compton emission (Eckart et al. 2004; Yusef-Zadeh et al. 2006; Dodds-Eden et al. 2009).”
• An X-Ray, Infrared, and Submillimeter Flare of Sagittarius A* (2007, methodology): “To date, a handful of events have been detected simultaneously in X-rays and the IR (Eckart et al. 2004, 2006b; Yusef-Zadeh et al. 2006b), yet because the IR and X-ray flares are observed to be simultaneous the flare evolution has received less attention than the peak spectra.”