A Plasmoid Model for the Sgr A* Flares Observed with GRAVITY and Chandra

Abstract

The Galactic Center black hole Sgr A* shows significant variability and flares in the submillimeter, infrared, and X-ray wavelengths. Owing to its exquisite resolution in the IR bands, the GRAVITY experiment for the first time spatially resolved the locations of three flares and showed that a bright region moves in ellipse-like trajectories close to but offset from the black hole over the course of each event. We present a model for plasmoids that form during reconnection events and orbit in the coronal region around a black hole to explain these observations. We utilize general-relativistic radiative transfer calculations that include effects from finite light travel time, plasmoid motion, particle acceleration, and synchrotron cooling and obtain a rich structure in the flare lightcurves. This model can naturally account for the observed motion of the bright regions observed by the GRAVITY experiment and the offset between the center of the centroid motion and the position of the black hole. It also explains why some flares may be double-peaked while others have only a single peak and uncovers a correlation between the structure in the lightcurve and the location of the flare. Finally, we make predictions for future observations of flares from the inner accretion flow of Sgr A* that will provide a test of this model.

10 pages, 9 figures

References in corpus (8)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks
• Plasma diagnostic potential of 2p4f in N${}^{+}$ -- accurate wavelengths and oscillator strengths
• The Power of Imaging: Constraining the Plasma Properties of GRMHD Simulations using EHT Observations of Sgr A*
• Modeling the orbital motion of Sgr A*'s near-infrared flares
• Plasmoid formation in global GRMHD simulations and AGN flares
• Time Dependent Models of Flares from Sagittarius A*
• A Cool Accretion Disk around the Galactic Centre Black Hole

Cited by in corpus (12)

• Flares in the Galactic center I: orbiting flux tubes in Magnetically Arrested Black Hole Accretion Disks
• Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc
• General relativistic MHD simulations of non-thermal flaring in Sagittarius A*
• Spinning black holes magnetically connected to a Keplerian disk -- Magnetosphere, reconnection sheet, particle acceleration and coronal heating
• Polarimetric signatures of hot spots in black hole accretion flows
• Positron Effects on Polarized Images and Spectra from Jet and Accretion Flow Models of M87* and Sgr A*
• Accretion Flow Morphology in Numerical Simulations of Black Holes from the ngEHT Model Library: The Impact of Radiation Physics
• Synchrotron Firehose Instability
• Electromagnetic signatures of strong-field gravity from accreting black holes
• The Effects of Tilt on the Time Variability of Millimeter and Infrared Emission from Sagittarius A*
• Radiative energy from a reconnection region around massive black hole
• Persistent time lags in light curves of Sagittarius A*: evidence of outflow