AAS Meeting #193 - Austin, Texas, January 1999
Session 56. HEAD II: Exotic Neutron Stars
Division, Oral, Thursday, January 7, 1999, 2:00-3:30pm, Ballroom A

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[56.02] Soft Gamma-ray Repeaters

C. Kouveliotou (USRA at NASA/MSFC)

Soft Gamma Repeaters (SGRs) are sources of brief intense outbursts of low-energy \gamma radiation, which occur in bunches, with active periods lasting between few weeks and several months at time intervals of years. Three SGRs were discovered between 1979 and 1983 and a fourth in 1998. Their (rudimentary) sky distribution (three very close to the galactic plane in the central regions of the Galaxy, the fourth in the LMC) indicates that peak luminosities of SGR bursts are in the range 1042 to 1044 erg/s and suggests that SGRs are a young source population, a conclusion supported by the stregthening association of SGRs with young supernova remnants.

In early 1998 we discovered X-ray pulsations from two SGRs: SGR~1806-20 and SGR~1900+14, with periods of 7.47 and 5.16 s, respectively. Subsequent observations revealed a significant spindown of these periods, of the order of 10-10 s/s in both cases. The P and \dot{P} measurements allowed us to conclude that SGRs are magnetars, i.e., young neutron stars with very strong magnetic fields of B>1014 G. I will describe the SGR overal characteristics and discuss the evidence that link SGRs to magnetars.

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