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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[56.04] Magnetar Models for Soft Gamma Repeaters and Anomalous X-ray Pulsars

R.C. Duncan (University of Texas at Austin)

I will review the evidence which seems to indicate that Soft Gamma Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs) are neutron stars with magnetic fields much stronger than BQ = 4.4 X 1013 G. Such hypothetical stars have been called "magnetars" because their observable emissions are powered by magnetism. The evidence for magnetars includes: (1) rotation periods, ages and spindown rates of SGRs and AXPs; (2) statistical distributions of SGR burst energies and waiting times, and their (cross) correlations, which agree with the predictions of magnetically-induced starquake models; (3) hyper-Eddington SGR bursts with simple light curves, as expected for starquake emissions when Compton scattering is strongly suppressed by a B >> BQ field; (4) properties of the "giant bursts" observed on March 5, 1979 and August 27, 1998, which give evidence for magnetic instabilities and reconnection; (5) X-ray afterglows from bursts; (6) quasi-steady X-ray and relativistic particle emissions; and (7) large recoil velocities in some SGRs, which could be due to magnetically-induced anisotropic neutrino emissions. Each of these areas is the subject of ongoing research. I will highlight some of the many challenging physics problems which remain to be solved. I will also discuss the theory of magnetar formation via dynamo action in nascent neutron stars, and current observational & theoretical constraints on the over-all magnetic field distribution of first-generation neutron stars.


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