Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* From Strong-Field Gravitational Lensing
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CitationChan, Chi-kwan, Dimitrios Psaltis, Feryal Özel, Lia Medeiros, Daniel Marrone, Aleksander Sadowski, and Ramesh Narayan. 2015. “Fast Variability and Millimeter/IR Flares in GRMHD Models of Sgr A* From Strong-Field Gravitational Lensing.” The Astrophysical Journal 812 (2) (October 13): 103. doi:10.1088/0004-637x/812/2/103.
AbstractWe explore the variability properties of long, high cadence GRMHD simulations across the electromagnetic spectrum using an efficient, GPU-based radiative transfer algorithm. We focus on both disk- and jet-dominated simulations with parameters that successfully reproduce the time-averaged spectral properties of Sgr A∗ and the size of its image at 1.3 mm. We find that the disk-dominated models produce short timescale variability with amplitudes and power spectra that closely resemble those inferred observationally. In contrast, jet-dominated models generate only slow variability, at lower flux levels. Neither set of models show any X-ray flares, which most likely indicate that additional physics, such as particle acceleration mechanisms, need to be incorporated into the GRMHD simulations to account for them. The disk-dominated models show strong, short-lived mm/IR flares, with short (. 1 hr) time lags between the mm and IR wavelengths, that arise from strong-field gravitational lensing of magnetic flux tubes near the horizon. Such events provide a natural explanation for the observed IR flares with no X-ray counterparts.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:27772999
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