Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity

Abstract

Sgr A*, the massive black hole at the center of the Galaxy, varies in radio through X-ray emission on hourly time scales. The flare activity is thought to arise from the innermost region of an accretion flow onto Sgr A*. We present simultaneous light curves of Sgr A* in radio, sub-mm and X-rays that show a possible time delay of 110$\pm 17$ minutes between X-ray and 850 $\mu$m suggesting that the sub-mm flare emission is optically thick. At radio wavelengths, we detect time lags of of $20.4\pm 6.8,30\pm 12$ and 20$\pm 6$ minutes between the flare peaks observed at 13 and 7 mm (22 and 43 GHz) in three different epochs using the VLA. Linear polarization of 1$\pm 0.2$% and 0.7$\pm 0.1$% is detected at 7 and 13 mm, respectively, when averaged over the entire observation on 2006 July 17. A simple model of a bubble of synchrotron emitting electrons cooling via adiabatic expansion can explain the time delay between various wavelengths, the asymmetric shape of the light curves, and the observed polarization of the flare emission at 43 and 22 GHz. The derived physical quantities that characterize the emission give an expansion speed of v${}_{exp}\sim 0.003-0.1$c, magnetic field of B$\sim$10-70 Gauss and particle spectral index p$\sim$1-2. These parameters suggest that the associated plasma cannot escape from Sgr A* unless it has a large bulk motion.

28 pages, 9 figures, 2 tables, ApJ July 20, 2008

References in corpus (5)

• Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
• A Constant Spectral Index for Sagittarius A* During Infrared/X-ray Intensity Variations
• A Testable the Stochastic Acceleration Model for Flares in Sagittarius A*
• The Variability of Polarized Radiation from Sgr A*
• Constraining Radiatively Inefficient Accretion Flows with Polarization

Cited by in corpus (38)

• The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA
• Millimeter light curves of Sagittarius A* observed during the 2017 Event Horizon Telescope campaign
• Time Dependent Models of Flares from Sagittarius A*
• Tidal effects on small bodies by massive black holes
• NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A* flares
• Where do the 3.5 keV photons come from? A morphological study of the Galactic Center and of Perseus
• Simultaneous NIR/sub-mm observation of flare emission from SgrA*
• Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
• Rapid Variability of Sgr A* across the Electromagnetic Spectrum
• Sgr A* X-ray flares from non-thermal particle acceleration in a magnetically arrested disc
• ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
• A 600 minute near-infrared lightcurve of Sagittarius A*
• Constraining particle acceleration in Sgr A* with simultaneous GRAVITY, Spitzer, NuSTAR and Chandra observations
• The Quiescent X-ray Spectrum of Accreting Black Holes
• Polarized light from Sgr A* in the near-infrared $K_s$-band
• Effect of Electromagnetic Interaction on Galactic Center Flare Components
• Exploring plasma evolution during Sagittarius A* flares
• Coordinated NIR/mm observations of flare emission from Sagittarius A*
• Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA
• A Possible Model for the Long-Term Flares of Sgr A*
• The variability of Sagittarius A* at 3 millimeter
• Simultaneous Monitoring of X-ray and Radio Variability in Sagittarius A*
• Flares and their echoes can help distinguish photon rings from black holes with space-Earth very long baseline interferometry
• A nonthermal bomb explains the near-infrared superflare of Sgr A*
• Multi-wavelength Observations of Sgr A*. I. 2019 July 18
• AzTEC Survey of the Central Molecular Zone: Data Reduction, Analysis, and Preliminary Results
• Continuation of the X-ray monitoring of Sgr A*: the increase in bright flaring rate confirmed
• Radiative shock oscillation model for the long-term flares of Sgr A*
• A Swift study of long-term changes in the X-ray flaring properties of Sagittarius A*
• Polarized signatures of adiabatically expanding hotspots in Sgr A*'s accretion flow
• Magnetic flux eruptions at the root of time-lags in low-luminosity AGN
• Detection of a 20 minute time lag observed from Sgr A* between 8 and 10 GHz with the VLA
• Short Timescale Evolution of the Polarized Radio Jet during V404 Cygni's 2015 Outburst
• Time delays between radio and X-ray and between narrow radio bands of Sgr A* flares in the shock oscillation model
• The Core-shift of Sagittarius A* as a Discriminant between Disk and Jet Emission Models with millimeter-VLBI
• SgrA* emission at 7mm: variability and periodicity
• Flaremodel: An open-source Python package for one-zone numerical modelling of synchrotron sources
• Full-polarization millimeter wavelength variability of Sagittarius A* during the 2018 EHT campaign