Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sgr A*

Abstract

The radiative counterpart of the supermassive black hole at the Galactic center (GC), Sgr A*, is subject to frequent flares visible simultaneously in X-rays and near-infrared (NIR). Often, enhanced radio variability from centimeter to sub-millimeter wavelengths is observed to follow these X-ray/NIR eruptions. We present here a multi-wavelength campaign carried out in April 2009, with the aim of characterizing this broadband flaring activity. Concurrent data from the XMM-Newton/EPIC (2-10 keV), VLT/NACO (2.1 microns, 3.8 microns), APEX/LABOCA (870 microns), and Fermi/LAT (0.1-200 GeV) instruments are employed to derive light curves and spectral energy distributions of new flares from Sgr A*. We detected two relatively bright NIR flares both associated with weak X-ray activity, one of which was followed by a strong sub-mm outburst 200 min later. Photometric spectral information on a NIR flare was obtained for the first time with NACO giving a power-law photon index alpha=-0.4\pm0.3. The first attempt to detect flaring activity from the Fermi GC source 1FGL J1745.6-2900 is also reported. NIR, X-ray, and sub-mm flares are finally modeled in the context of non-thermal emission processes. It is found that the simplest scenario involving a single expanding plasmoid releasing synchrotron NIR/sub-mm and synchrotron self-Compton X-ray radiation is inadequate to reproduce the data, but suggestions to reconcile the basic elements of the theory and the observations are proposed.

13 pages, 11 figures, accepted for publication in Astronomy and Astrophysics, typos corrected

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• The Disc-Jet Symbiosis Emerges: Modeling the Emission of Sagittarius A* with Electron Thermodynamics
• A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission
• Sgr A* and General Relativity
• The XMM-Newton view of the central degrees of the Milky Way
• Variability Timescale and Spectral Index of Sgr A* in the Near Infrared: Approximate Bayesian Computation Analysis of the Variability of the Closest Supermassive Black Hole
• Fifteen years of XMM-Newton and Chandra monitoring of Sgr A*: Evidence for a recent increase in the bright flaring rate
• Sgr A* flares: tidal disruption of asteroids and planets?
• NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A* flares
• Distinguishing black holes and wormholes with orbiting hot spots
• Galactic Center Research: Manifestations of the Central Black Hole
• Rapid Variability of Sgr A* across the Electromagnetic Spectrum
• Constraining particle acceleration in Sgr A* with simultaneous GRAVITY, Spitzer, NuSTAR and Chandra observations
• The X-ray Flux Distribution of Sagittarius A* as Seen by Chandra
• The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
• The Intrinsic Two-Dimensional Size of Sagittarius A*
• A comparison of the R_h=ct and LCDM cosmologies using the Cosmic Distance Duality Relation
• On the Fe K absorption - accretion state connection in the Galactic center neutron star X-ray binary AX J1745.6-2901
• Near-Infrared and X-ray Quasi-Periodic Oscillations in Numerical Models of Sgr A*
• Simultaneous X-ray and Infrared Observations of Sagittarius A*'s Variability
• Statistics of X-ray flares of Sagittarius A*: evidence for solar-like self-organized criticality phenomenon
• An Inverse Compton Scattering Origin of X-ray Flares from Sgr A*
• A Systematic Chandra study of Sgr A${}^{\star }$: I. X-ray flare detection
• Multiwavelength Light Curves of Two Remarkable Sagittarius A* Flares
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• Multiwavelength study of the flaring activity of Sgr A* in 2014 February-April
• Sagittarius A* High Energy X-ray Flare Properties During NuSTAR Monitoring of the Galactic Center from 2012 to 2015
• Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots
• Flares and variability from Sagittarius A*: five nights of simultaneous multi-wavelength observations
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• A Leptonic Model of Steady High-Energy Gamma-Ray Emission from Sgr A${}^{\ast }$
• Flares and their echoes can help distinguish photon rings from black holes with space-Earth very long baseline interferometry
• Multi-wavelength Variability of Sagittarius A* in July 2019
• Testing a class of non-Kerr metrics with hot spots orbiting SgrA${}^{\ast }$
• Constraining the Cardoso-Pani-Rico metric with future observations of SgrA${}^{\ast }$
• Time Domain Filtering of Resolved Images of Sgr A*
• A Swift study of long-term changes in the X-ray flaring properties of Sagittarius A*
• Flare emission from Sagittarius A*
• Unseen Progenitors of Luminous High-z Quasars in the R_h=ct Universe
• Possible evidence from the flaring activity of Sgr A* for a star at a distance of ~3.3 Schwarzscild radii from the blackhole
• New Evidence for a Flux-independent Spectral Index of Sgr A* in the Near-infrared
• The orbit and nature of the semi-detached stellar companion of Sgr A* super-massive blackhole
• Polarimetric Imaging of Sgr A* in its Flaring State
• High Energy Emission from the Galactic Center
• Variability of Sagittarius A* at 3 GHz on minute-scale with MeerKAT