PROBING RELATIVISTIC WINDS: THE CASE OF PSR J07370-3039 A & B

We propose synchrotron absorption in a magnetosheath forming a cocoon aroundthe magnetosphere of pulsar B to be the origin of the eclipse phenomena seen inthe recently discovered double pulsar system PSRJ07370-3039 A & B. The modelpredicts the eclipses will clear at frequencies higher than those of theobservations reported to date (nominally, above $\nu \sim 5$ GHz.) The modelalso predicts synchrotron emission at the level of a few to 10 $\mu$Jy, peakingat $\nu \sim 2-5$ GHz with possible orbital modulation. We use simplifiedsemi-analytic models and particle-in-cell simulations to elucidate thestructure of the B magnetosphere, showing that B's magnetic field is confinedto within a radius less than 50,000 km from B,on the side facing A. We estimatea ``propellor'' spindown torque on B, which is the dominant torque on thisstar, which yields a polar dipole field $\sim 7 \times 10^{11}$ Gauss (magneticmoment $\mu_B \sim 3.5 \times 10^{29}$ cgs). The model can explain the knowneclipses only if the A wind's density is at least 4 orders of magnitude greaterthan is expected from popular pair creation models, and discuss theimplications of this result for our general understanding of pulsar physics.Our proposal was outlined in Kaspi et al. (2004) and Demorest et al. (2004); asimilar proposal has been made by Lyutikov (2004).