X-ray Pulsations from the Central Source in Puppis A

There are several supernova remnants which contain unresolved X-ray sources close to their centers, presumably radio-quiet neutron stars. To prove that these objects are indeed neutron stars, to understand the origin of their X-ray radiation, and to explain why they are radio-quiet, one should know their periods and period derivatives. We searched for pulsations of the X-ray flux from the radio-quiet neutron star candidate RX J0822–4300 near the center of the Puppis A supernova remnant observed with the ROSAT PSPC and HRI. A standard timing analysis of the separate PSPC and HRI data sets does not allow one to detect the periodicity unequivocally. However, a thorough analysis of the two observations separated by 4.56 yr enabled us to find a statistically significant period P ' 75.3 ms and its derivative Ṗ ' 1.49 × 10−13 s s−1. The corresponding characteristic parameters of the neutron star, age τ = P/(2Ṗ ) = 8.0 kyr, magnetic field B = 3.4 × 1012 G, and rotational energy loss Ė = 1.4 × 1037 erg s−1, are typical for young radio pulsars. Since the X-ray radiation has a thermal-like spectrum, its pulsations may be due to a nonuniform temperature distribution over the neutron star surface caused by anisotropy of the heat conduction in the strongly magnetized crust. Subject headings: pulsars: individual (RX J0822–4300) – stars: neutron – supernovae: individual (Puppis A) – X-rays: stars