TeV gamma-rays from accreting magnetars in massive binaries

Abstract

We consider the neutron star (NS) of the magnetar type inside the massive binary system. We determine the conditions under which the matter from the stellar wind can penetrate the inner magnetosphere of the magnetar. At some distance from the NS surface, the magnetic pressure can balance the gravitational pressure of the accreting matter creating very turbulent, magnetized transition region. It is suggested that this region provides good conditions for acceleration of electrons to relativistic energies. These electrons lose energy on the synchrotron process and the Inverse Compton (IC) scattering of the radiation from the nearby massive stellar companion, producing high energy radiation from the X-rays up to $\sim$TeV $\gamma$-rays. The primary $\gamma$-rays can be farther absorbed in the stellar radiation developing the IC $e^\pm$ pair cascade. We calculate the synchrotron X-ray emission from primary electrons and secondary $e^\pm$ pairs and the IC $\gamma$-ray emission from the cascade process. It is shown that the quasi-simultaneous observations of the TeV $\gamma$-ray binary system LSI +61 303 in the X-ray and the TeV $\gamma$-ray energy ranges can be explained in such an accreting magnetar model.