A Possible Origin of Gamma Ray Bursts and Axionic Boson Stars

We indicate a possible mechanism of generating gamma ray bursts. They are generated by a collision between an axionic boson star and a neutron star. The axionic boson star can dissipates its whole energy $10^{50}$ erg in the magnetized conducting medium of the neutron star. This dissipation arises only around envelope of the neutron star so that a fire ball with small baryon contamination is expected. We have evaluated roughly a rate of the collision per year and per galaxy which is consistent with observations, under plausible assumptions. We also point out that cosmic rays with extremely high energy, $10^{21}$eV, can be produced in the similar collisions with the neutron stars with strong magnetic fields $\sim 10^{14}$G.