Interstellar scintillation of the double pulsar J0737-3039: effects of anisotropy

Abstract

We describe a year-long series of interstellar scintillation (ISS) observations of the double pulsar using the Green Bank Telescope. The goal is to improve the estimates of the proper motion velocity of this interesting binary system relative to the interstellar plasma. The scintillation time scale varies remarkably over its orbital period but only provides three independent parameters per epoch. Extra information is found from repeating these observations over a year, as the Earth velocity changes, and also from cross-correlating the scintillations of the two pulsars. The latter gives clear evidence that the ISS is anisotropic with an axial ratio greater than 2.6. This reduces the proper motion velocity over that obtained assuming isotropic ISS. However, changes in the timing of the orbital windows when the slow pulsar is detectable have limited the usefulness of this technique. A progress report on the work is presented.

Keywords:

• Interstellar scintillation
• Binary pulsar system
• Anisotropy