7.4.3 The Fate of the Binary System

Fig. 7.16 The double pulsar system PSR J0737-3039A/B, in the representation of an artist

7.4.4 The Double Pulsar

December 12th 2003, on journals and on the Internet appeared the official announcement of a new exciting discovery. An international team of radio-astronomers, including a strong and driving group of Italians,7 found the the Double Pulsar system officially named PSR J0737-3039A/B (see Fig. 7.16). This system is quite similar to the system PSR1913+16 but it has some additional features that make it an extraordinary precise laboratory to test General Relativity and Neutron Star Physics under extreme strong field conditions. The relevant data are displayed in Table 7.2. The first feature, in contrast with the case of PSR1913+16 is that both members of PSR J0737-3039A/B are pulsars and therefore they are both directly detectable. The second notable feature of the system is its extreme narrowness which emphasizes all General Relativity effects. The orbit has low eccentricity but the semilatus rectum is less than a million of Kilometers which results in a revolution period of just 2.4 hours. The periastron advance is accordingly very high and its measured value perfectly fits the predictions of General Relativity. Similarly the shortness of the revolution period allowed a rapid measure of its shrinking with very high statistics and the indirect evidence of the emission of gravitational waves was tested once again in excellent agreement with General Relativity. Using the measured parameters we

7The Italian Team participating to the discovery is constituted by members of INAF, the Istituto Nazionale di Astrofisica, belonging to the Cagliari Pulsar Group and to the Universities of Cagliari and Bologna, including Marta Burgay, Andrea Possenti and Nichi d’Amico. The main international partners of the collaboration were the Jodrell Bank pulsar group in Manchester, the ATNF pulsar group in Sydney (Australia) and the Swinburne pulsar group also in Australia (Melbourne). Finally also the European Pulsar Timing Array collaboration was involved. The radio-telescope used for the discovery is the Parkes radio telescope in Australia (see Fig. 7.17). Further observations were carried on at the Northern Cross radio-telescope near Bologna in Italy and in other European radio observatories.