Radio Non-Detection of the SGR 1806-20 Giant Flare and Implications for Fast Radio Bursts

Shriharsh P. Tendulkar, Victoria M. Kaspi, Chitrang Patel

Published 2016-02-05Version 1

We analyse archival data from the Parkes radio telescope which was observing a location 35.6$^\circ$ away from SGR 1806-20 during its giant $\gamma$-ray flare of 2004 December 27. We show that no FRB-like burst counterpart was detected, and set a radio limit of 11 MJy at 1.4 GHz, including the suppression of the signal due to the predicted scattering and its location in the far side lobe of Parkes. A conservative upper limit for the magnetar giant flare radio to $\gamma$-ray fluence ratio is $\eta_\mathrm{SGR}<10^{6.9}\,\mathrm{Jy\,ms\,erg^{-1}\,cm^{2}}$. Based on the non-detection of a short and prompt $\gamma$-ray counterpart of fifteen FRBs in $\gamma$-ray transient monitors, we set a lower limit on the fluence ratios of FRBs to be $\eta_\mathrm{FRB} >10^{6.8-8.9}\,\mathrm{Jy\,ms\,erg^{-1}\,cm^{2}}$. The fluence ratio limit for SGR 1806-20 is inconsistent with all but one of the fifteen FRBs. We discuss possible variations in the magnetar-FRB emission mechanism and observational caveats that may reconcile the theory with observations.