TeV photons and Neutrinos from giant soft-gamma repeaters flares

TL;DR

This paper explores the potential of detecting TeV gamma-rays and neutrinos from giant flares of Soft Gamma Repeaters using current and upcoming neutrino telescopes, estimating detection rates and implications for cosmic ray acceleration.

Contribution

It provides the first estimates of TeV gamma-ray and neutrino signals from SGR flares for detectors like AMANDA and Milagro, highlighting their potential to observe such high-energy emissions.

Findings

AMANDA could have detected the 2004 SGR 1806-20 flare if TeV emission extended to that energy.

Detection rates increase significantly in larger km3-scale detectors like IceCube.

SGR flares could be important sources of high-energy cosmic rays and neutrinos.

Abstract

During the last 35 years three giant flares were observed from so-called Soft Gamma Repeaters (SGR's). They are assumed to be associated with star-quakes of pulsars accelerating electrons and, possibly, protons to high energy in the huge magnetic fields as inferred from the observations. Because of this and the observation of non-thermal emission it has been speculated that they may be cosmic ray accelerators producing gamma-rays up to TeV energies. Neutrino telescopes, such as AMANDA and the ANTARES now under construction, could be used as TeV-gamma detectors for very short emissions by measuring underground muons produced in $\gamma$ showers. We estimate signal and background rates for TeV photons from SGR giant flares in AMANDA, and we provide an estimate of the gamma shower events that Milagro could detect. Moreover, we consider that, if hadrons are accelerated in these sources, high energy neutrinos would be produced together with photons. These may be detected in neutrino telescopes using neutrino-induced cascades and upgoing muons. We argue that the Antarctic Muon and Neutrino Detector Array AMANDA may have observed the December 27, 2004 giant flare from the soft gamma-ray repeater SGR 1806-20 if the non-thermal component of the spectrum extends to TeV energies (at present the actual data is subject to blind analysis). Rates should be scaled by about two orders of magnitude in km3 detectors, such as IceCube, making SGR flares sources of primary interest.