Magnetic field and EOS effects on axion emission from the non-rotating neutron stars

Abstract

We present here a comparative study of different axion emission mechanism from the core of highly magnetized neutron stars. In this work, it is assumed that neutron stars is being cooled as a consequence of the emission of neutrinos and axionic dark matter particles from the core of the neutron stars. We employ three different equation of states APR, FPS,SLY to solve the modified TOV equations, determine the mass and the pressure profiles by assuming that core of Neutron Stars to be made up of a hadronic matter. By employing above profiles, we obtain the cooling rate of spherically symmetric NSs with and without magnetic field to see the impact of magnetic field employing the different equation of states. The same is also studied with and without considering axion emission within the star core. Luminosities of axions as a dark matter candidates, neutrinos and photons have been plotted as a function of time with and without magnetic field. A fraction of these axions may undergo photon conversion in the powerful magnetic field within NSs magnetosphere, producing broadband radio or X-ray waves. Finally, we show the effect of magnetic field within the possible axion mass range on the actual observables such as total X-ray flux and conversion probability as a result of different axion to photon conversion mechanisms.