ON THE ORIGIN OF EXTRAGALACTIC GAMMA-RAY BURSTERS

In the frame of the two-fluid model of extragalactic radio sources, th e properties of extragalactic gamma-ray bursters can be explained by t he emission of a precessing relativistic e(+/-) beam whose bulk Lorent z factor is gamma(b) similar or equal to 10. The gamma-ray emission of the ejected e(+/-) component has a non-thermal origin and is due to t he e(+/-) annihilations and the inverse Compton losses. Due to the rel ativistic motion of the e(+/-) component, its emission is strongly ani sotropic. When several peaks are observed, the typical time scale betw een the peaks is of a few seconds and it corresponds to a perturbation period of the beam of about P-o similar or equal to 100 s. This high frequency perturbation corresponds to the rotation frequency of a comp act object turning at almost 3 Schwarzschild radii around a central bl ack hole of mass 10(5) M(.) less than or equal to M less than or equal to 10(6) M(.). The rotating compact object perturbs the accretion dis k around the black hole and the frozen magnetic field of the jet. It i nduces a precession of the beam and an e(+/-) component is ejected rel ativistically in the precessing beam producing a gamma-ray emission wh ich appears to be pulsating for the observer. Due to the rotation of t he compact object the system emits gravitational waves together with t he gamma-ray emission. Finally, gamma-ray bursters are associated with distant normal galaxies and after few months we expect an anisotropic radio emission whose flux density is S-v less than or equal to 0.15 m Jy if the redshift of the galaxy is z greater than or equal to 0.2.