General Properties of Recurrent Bursts from SGRs
General properties of SGR bursts are considered using observational data collected in the Konus catalog of SGR activity.
arXiv subjects
Publications and source records attributed to S. V. Golenetskii.
General properties of SGR bursts are considered using observational data collected in the Konus catalog of SGR activity.
Fast spectral variability of gamma-ray burst emission is considered for a number of events seen by the Konus-Wind experiment. The variability manifests itself as a strong correlation between instantaneous energy flux $F$ and peak energy $E_p$. In the ($F,E_p$) plane, the correlation produces distinct tracks in the form of branches and loops representing the different parts of a burst time history. Despite the variety of features seen in different events, the main characteristics of the spectral evolution produce a quite consistent pattern.
Observational data on the bursting activity of all five known Soft Gamma Repeaters are presented. This information was obtained with Konus gamma-ray burst experiments on board Venera 11-14, Wind, and Kosmos-2326 spacecraft in the period from 1978 to 2000. These data on appearance rates, time histories, and energy spectra of repeated soft bursts obtained with similar instruments and collected together in a comparable form should be useful for further studies of SGRs. (available at http://www.ioffe.rssi.ru/LEA/SGR/Catalog/).
Results are presented of the observations of the soft gamma repeater SGR 1900+14 made on the Wind spacecraft during the source reactivation period from May 1998 to January 1999. Individual characteristics of recurrent bursts, such as their time histories, energy spectra, and maximum and integrated energy fluxes, are considered. Some statistical distributions and relationships are also presented. The close similarity of these events to the recurrent bursts observed from other SGRs argues for a common emission mechanism.
The results of observations of the giant 1998 August 27 outburst in SGR 1900+14 are presented. A comparison is made of the two extremely intense events on August 27, 1998 and March 5, 1979. The striking similarity between the outbursts strongly implies a common nature. The observation of two giant outbursts within 20 years from different sources suggests that such events occur in an SGR once every 50-100 years.
In June-July,1998 the Konus-Wind burst spectrometer observed a series of bursts from the new soft gamma repeater SGR1627-41. Time histories and energy spectra of the bursts have been studied, revealing fluences and peak fluxes in the ranges of 3x10^{-7} - 7.5x10^{-6} erg cm^{-2} and 10^{-5} - 10^{-4}erg cm^{-2}/s respectively. One event, 18 June 6153.5sUT stands out dramatically from this series. Its fluence is ~7x10^{-4} erg cm^{-2} and peak flux ~2x10^{-2} erg cm^{-2}/s. These values from a source at a distance of 5.8 kpc yield an energy output of ~3x10^{42}erg and maximum luminosity of ~8x10^{43} erg/s, similar to the values for the famous March 5, 1979 and August27,1998 events. In terms of energy, this event is another giant outburst seen in a third SGR! However, this very energetic burst differs significantly from the other giant outbursts. It exhibits no separate initial pulse with a fast rise time, no extended tail, and no pulsations. It is rather similar to ordinary repeated bursts but is a few hundred times stronger in intensity. According to the magnetar model by Thompson and Duncan (1995) such a burst may be initiated by a strong starquake when a crust fracture propagates over the whole surface of a neutron star.