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 1050 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. Under plausible assumptions we have evaluated roughly a rate of the collision per year and per galaxy, which is consistent with observations. We also point out that cosmic rays with extremely high energy, 1021 eV, can be produced in the similar collisions with the neutron stars with strong magnetic fields ∼1014 G.