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K. Hurley, J. McTiernan (UC Berkeley Space Sciences Lab.), T. Cline, S. Barthelmy, P. Butterworth, F. E. Marshall, D. Palmer, J. Trombka (NASA GSFC), E. Mazets, R. Aptekar, S. Golenetskii, V. Il'inskii, D. Frederiks (Ioffe Physical-Technical Institute, St. Petersburg, Russia), R. Gold (JHU-APL)
The most intense burst of X- and gamma-radiation in 30 years of monitoring was observed on August 27 1998 by seven spacecraft. It came from the soft gamma repeater SGR1900+14. Like the March 5 1979 burst from SGR0525-66, it displayed a hard, short peak followed by a soft, long pulsating tail. The period of the pulsations, 5.16 s, is identical to the period of a quiescent soft X-ray source previously proposed as the counterpart to this SGR. In the magnetar model, the initial peak was probably caused by massive, large-scale cracking of the neutron star crust, while the soft tail is due to a hot plasma trapped in magnetosphere. This leads to an estimate of the magnetic field strength based on the energy in the soft tail, which is B>1014 G.