A Giant Flare from a Soft Gamma Repeater in the Andromeda Galaxy, M31

TL;DR

This paper reports the detection and analysis of a giant flare from a soft gamma repeater in the Andromeda Galaxy, providing detailed spectral and energetic measurements that align with known SGR flares.

Contribution

The study presents the first identification of a giant flare from a soft gamma repeater in M31, with detailed spectral, energetic, and localization data supporting its classification.

Findings

Flare energy estimated at 1.5 x 10^45 erg.

Localization consistent with M31 galaxy.

Flare characteristics match previous SGR giant flares.

Abstract

The light curve, energy spectra, energetics, and IPN localization of an exceedingly intense short duration hard spectrum burst, GRB 070201, obtained from Konus-Wind, INTEGRAL (SPI-ACS), and MESSENGER data are presented. The total fluence of the burst and the peak flux are $S = 2.00_{-0.26}^{+0.10} \times 10^{-5}$ erg cm$^{-2}$ and $F_{max} = 1.61_{-0.50}^{+0.29} \times 10^{-3}$ erg cm$^{-2}$ s$^{-1}$. The IPN error box has an area of 446 square arcminutes and covers the peripheral part of the M31 galaxy. Assuming that the source of the burst is indeed in M31 at a distance of 0.78 Mpc, the measured values of the fluence $S$ and maximum flux $F_{max}$ correspond to a total energy of $Q = 1.5 \times 10^{45}$ erg, and a maximum luminosity $L = 1.2 \times 10^{47}$ erg s$^{-1}$. These data are in good agreement with the corresponding characteristics of the previously observed giant flares from other soft gamma repeaters. The evidence for the identification of this event as a giant flare from a soft gamma repeater in the M31 galaxy is presented.