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Fast Variability and mm/IR flares in GRMHD Models of Sgr A* from Strong-Field Gravitational Lensing by Chan, Chi-kwan; Psaltis, Dimitrios; Ozel, Feryal; Medeiros, Lia; Marrone, Daniel; Sadowski, Aleksander; Narayan, Ramesh is a scholarly article available to read on EtoBox.

What is Fast Variability and mm/IR flares in GRMHD Models of Sgr A* from Strong-Field Gravitational Lensing about?

We 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 1.3mm. 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 (<~ 1hr) 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.

Author

Chan, Chi-kwan; Psaltis, Dimitrios; Ozel, Feryal; Medeiros, Lia; Marrone, Daniel; Sadowski, Aleksander; Narayan, Ramesh

Published

2015

Language

EN