A tool for probing the structure of neutron stars: Transient X-ray emission

Abstract

We suggest that some galactic transient X-ray sources are actually very old neutron stars. An intense transient thermal X-ray flux will be emitted from these sources when a sudden period jump occurs. This phenomenon, called a glitch, results from either sudden angular momentum transfer from crustal superflid to the solid part of the star or sudden fracture of the crustal lattice due to gravitational stress. The excess of the rotation energy will be dissipated in terms of thermal radiation. Such transient X-ray emission should be detectable if the source is located within 1 kpc of the solar system. Most important, the evolution of a thermal X-ray transient can provide valuable information for the equation of state of the stars because the peak of the thermal flux and the characteristic timescales, e.g., the timescale to reach the X-ray flux peak, duration of the thermal pulse, and the timescale to reach the steady state, which are observable and are sensitive to the equation of state of neutron stars.