Gamma-ray bursts from X-ray binaries

A weakly magnetized (similar to 10(7) G) neutron star, slowly spun up by ac cretion in an X-ray binary, crosses the instability boundary for r-mode ins tability at P = 1-2 msec. The amplitude of the oscillation, which initially increases only at the spinup time scale, is secularly unstable due to the negative temperature dependence of the viscosity in neutron star matter, an d diverges after a few hundred years. Angular momentum loss by the gravitat ional wave causes strong differential rotation, in which the magnetic field is wound up to 10(17)G On a time scale of a few months. When this held bec omes unstable to buoyancy instability, a surface field strength of a few 10 (16)G is produced on a TEM = time scale of seconds, which then powers a GRB with energies of 10(51)-10(52) and duration of 1-100 sec.