Testing the rotating lighthouse model with the double pulsar system PSR J0737-3039A/B

Each of the two pulsars in the double pulsar PSR J0737-3039A/B system exhibits not only the pulses emanating from it, but also displays modulations near the pulse period of the other. Freire et al. (2009, MNRAS, 396, 1764) have put forward a technique using the modulation of B by A to determine the sense of rotation of pulsar A relative to its orbital motion, among other quantities. In this paper, we present another technique with the same purpose. While the Freire et al. approach analyses pulse arrival times, ours instead uses periods or frequencies (their inverses), which can be experimentally determined via power spectral analysis similar to that used in pulsar searches. Our technique is based on the apparent change in spin period of a body when it is measured from an orbiting platform (the other pulsar), and is shown to be entirely analogous to the difference between the sidereal and solar spin period of the Earth (i.e. the sidereal and solar day). Two benefits of this approach are its conceptual and computational simplicity. The direct detection of spin with this technique will observationally validate the rotating lighthouse model of pulsar emission, while the detection of the relative directions of spin and orbital angular momenta has important evolutionary implications. Our technique can be used on other binary systems exhibiting mutually induced phenomena.