Comparative study of the two large flares from SGR1900+14 with theBeppoSAXGamma-Ray Burst Monitor

Abstract

Abstract. We report on spectral and temporal results of the 40-700 keV observations, obtained with the Gamma-Ray Burst Monitor (GRBM) on board BeppoSAX, of the two large flares from the Soft Gamma-ray Repeater SGR 1900+14 occurred on August 27, 1998 and April 18, 2001. From their intensity, fluence and duration, the first one was classified as "giant" and the second as "intermediate".The spectral results have been obtained with an improved response function of the GRBM. We find that the two events have similar spectral properties, but different temporal properties. The major difference concerns the time profiles of the light curves, whereas the lack of evidence in the 2001 flare for the erratic time variability found at high frequencies (10-1000 Hz) in the 1998 flare could be ascribed to lower counting statistics. We discuss these results in the light of the magnetar model proposed for SGR sources.

Pulsars and Magnetars

“…The strongest of these "intermediate" flares was observed on April 18, 2001 from SGR 1900+14 [108,74]. It lasted about 40 s and showed pulsations at the NS rotation period, as in the tails of giant flares, but it lacked an initial spike.…”

XMM–Newton observations of soft gamma-ray repeaters

“…Integrating over the entire flare assuming isotropic emission, at least 10 44 erg were released in hard X-rays above 15 keV (Mazets et al 1999). SGR 1900+14 also emitted another less intense flare on 18 April 2001 (Feroci et al 2003;Guidorzi et al 2004), which based on its energetics was classified as an "intermediate" flare.…”

Broadband X‐Ray Spectra of Short Bursts from SGR 1900+14

“…The luminosity of this giant burst was estimated to be greater than 10 44 ergs s À1 . Another very bright flare from SGR 1900+ 14 was observed on 2001 April 18 (Guidorzi et al 2004); it was shorter and less intense than that of 1998, but it too showed periodicity. Given that both its duration of $40 s and its peak luminosity of $10 42 ergs s À1 fell in between the common recurrent bursts and the giant flare, this burst was classified as an intermediate flare.…”