A giant flare from a soft gamma repeater in the Andromeda galaxy (M31)

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) x 10(-5) erg cm(-2) and F(max) = 1.61(-0.50)(+0.29) x 10(-3) erg cm(-2) s(-1). The IPN error box has an area of 446 arcmin(2) 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 x 10(45) erg and a maximum luminosity L = 1.2 x 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.