Population statistics study of radio and gamma-ray millisecond pulsars in the Galactic plane

We present results of our pulsar population synthesis of millisecond pulsars in the Galactic plane using our previously developed computer code. Over the past several years, a program has been developed to simulate pulsar birth, evolution and emission using Monte Carlo techniques. We have added to the program the capability to simulate millisecond pulsars, which are old, recycled pulsars with extremely short periods. We model the spatial distribution of millisecond pulsars by assuming that they start with a random kick velocity and then evolve through the Galactic potential set forth in Dehnen & Binney (1996). Their spin evolution starts along a spun-up birth line, with initial period correlated with surface magnetic field strength, randomly distributed above a minimum magnetic field of 2.6 × 10⁸ Gauss to give a minimum period of 0.65 ms following Cordes and Chernoff (1997). Using these initial parameters, we obtain fairly good agreement with known distributions of millisecond radio pulsars in the ˙ {P}-P diagram. We use polar cap/slot gap models for gamma-ray emission below/above the curvature radiation pair death line; this applies to both millisecond and ordinary pulsars. We present the preliminary results of our recent study and the implications for observing these pulsars with GLAST.

We express our gratitude for the generous support of the Michigan Space Grant Consortium, of Research Corporation (CC5813), of the National Science Foundation (REU and AST-0307365) and of the NASA Astrophysics Theory Program.