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تسجيل مستخدم جديدThe 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque
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We report on observations of SGR 1900+14 made with the Rossi X-ray Timing Explorer (RXTE) and BeppoSAX during the April 2001 burst activation of the source. Using these data, we measure the spindown torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to the gamma-ray profile during the April 18 intermediate flare and show that (i) their shapes are similar and (ii) the gamma-ray profile aligns closely in phase with the X-ray pulsations. The good phase alignment of the gamma-ray and X-ray profiles suggests that there was no rapid spindown following this flare of the magnitude inferred for the August 27 giant flare. We discuss how these observations further constrain magnetic field reconfiguration models for the large flares of SGRs.
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After nearly two years of quiescence, the soft gamma-ray repeater SGR 1900+14 again became burst-active on April 18 2001, when it emitted a large flare, preceded by few weak and soft short bursts. After having detected the X and gamma prompt emission
of the flare, BeppoSAX pointed its narrow field X-ray telescopes to the source in less than 8 hours. In this paper we present an analysis of the data from this and from a subsequent BeppoSAX observation, as well as from a set of RossiXTE observations. Our data show the detection of an X-ray afterglow from the source, most likely related to the large hard X-ray flare. In fact, the persistent flux from the source, in 2-10 keV, was initially found at a level $sim$5 times higher than the usual value. Assuming an underlying persistent (constant) emission, the decay of the excess flux can be reasonably well described by a t$^{-0.9}$ law. A temporal feature - a $sim$half a day long bump - is observed in the decay light curve approximately one day after the burst onset. This feature is unprecedented in SGR afterglows. We discuss our results in the context of previous observations of this source and derive implications for the physics of these objects.
After a couple of years of quiescence, the soft gamma repeater SGR 1900+14 suddenly reactivated on 18 April 2001, with the emission of a very intense, long and modulated flare, only second in intensity and duration to the 27 August 1998 giant flare.
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