Limits on the High-Energy Gamma and Neutrino Fluxes from the SGR 1806-20 Giant Flare of 27 December 2004 with the AMANDA-II Detector

On 27 December 2004, a giant $\gamma$ flare from the Soft Gamma-Ray Repeater 1806-20 saturated many satellite gamma-ray detectors, being the brightest transient event ever observed in the Galaxy. AMANDA-II was used to search for down-going muons indicative of high-energy gammas and/or neutrinos from this object. The data revealed no significant signal, so upper limits (at 90% C.L.) on the normalization constant were set: $0.05(0.5){\mathrm{TeV}}^{-1}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ for $\gamma =-1.47$ ($-2$) in the gamma flux and $0.4(6.1){\mathrm{TeV}}^{-1}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ for $\gamma =-1.47$ ($-2$) in the high-energy neutrino flux.

Figure 1

Effective area after reconstruction and track quality selection for gammas (solid black line) and neutrinos (dashed blue line).

Figure 2

Model discovery factor (solid black line) and model rejection factor (dashed red line) as a function of the radius of a circular angular acceptance window. The curves here are for a $E^{-1.47}$ spectrum.

Figure 3

Sensitivity (dashed red lines) and limit (solid black lines) to the normalization constant in the flux of gammas (lower line) and neutrinos (upper line), as a function of the spectral index, assuming a flux $\varphi (E)=A(E/\mathrm{TeV}{)}^{\gamma }$.