A Two-Component Explosion Model for the Giant Flare and Radio Afterglow from SGR1806-20

Abstract

The brightest giant flare from the soft $\gamma$-ray repeater (SGR) 1806-20 was detected on 2004 December 27. The isotropic-equivalent energy release of this burst is at least one order of magnitude more energetic than those of the two other SGR giant flares. Starting from about one week after the burst, a very bright ($\sim 80$ mJy), fading radio afterglow was detected. Follow-up observations revealed the multi-frequency light curves of the afterglow and the temporal evolution of the source size. Here we show that these observations can be understood in a two-component explosion model. In this model, one component is a relativistic collimated outflow responsible for the initial giant flare and the early afterglow, and another component is a subrelativistic wider outflow responsible for the late afterglow. We also discuss triggering mechanisms of these two components within the framework of the magnetar model.

arXiv comment7 pages including 3 figures, emulateapj5.sty, accepted for publication in ApJ Letters

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• Gamma-Ray Bursts in the Swift Era
• Possibility of Ultra High-Energy Cosmic Rays from the Giant Flare in SGR 1806-20
• Magnetar Giant Flare Originated GRB 200415A: Transient GeV emission, Time-Resolved ${\mathrm{E}}_{\mathrm{p}}-{\mathrm{L}}_{\mathrm{iso}}$ Correlation, and Implications
• Diffuse high energy neutrinos and cosmic rays from hyperflares of soft-gamma repeaters
• The Giant Flare from SGR 1806-20 and its Radio Afterglow
• AT2020hur: A Possible Optical Counterpart of FRB 180916B