New Test of Gravity Using Eclipses in the Double Pulsar PSR J0737-3039A/B

The double pulsar, the first relativistic binary in which both neutron stars are observable radio pulsars, is a celebrated laboratory for testing general relativity in the strong-field regime via the precise timing of its radio pulses. A very fortunate alignment of our sight line with the orbital plane of this system allows us to observe eclipses when one of the pulsars passes behind its companion. These eclipses display a complex structure of flux modulations that, according to a model proposed by Lyutikov and Thompson, originate from synchrotron absorption by plasma trapped in the magnetosphere surrounding the companion pulsar. We present four years of eclipse monitoring conducted at the Green Bank Telescope, with which we tested this eclipse model. Our work not only accurately reproduces the eclipse light curves using the Lyutikov and Thompson model, but also provides a quantitative measurement of relativistic spin precession of the companion pulsar. This qualitatively new test of gravity in the strong-field regime agrees remarkably well the value predicted by general relativity.