Strong-field tests of gravity with the double pulsar

This first-ever double-pulsar system was discovered in 2003, consisting of two visible pulsars which orbit the common centre of mass in a slightly eccentric orbit in only 2.4 hours. One of the pulsars appears to be old and recycled with a spin period of only 22 ms. Its companion is younger and rotating slower with a period of 2.8 s, confirming the long-proposed recycling theory for millisecond pulsars. The system provides an exciting opportunity to study the workings of pulsar magnetospheres and represents a truly unique laboratory for relativistic gravitational physics. Both aspects are greatly facilitated by the very fortunate fact that the orbit is seen nearly perfectly edge on. This alignment allows the detection of the Shapiro delay in the pulse arrival times of the 22-ms pulsar when its pulses propagate through the curved space-time near the slowly rotating pulsar. In addition to updating on the continuing observations, this contribution introduces a new timing model that represents a variation of Damour-Deruelle (1986) for highly inclined orbits. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.