1999ApJ...511L..45P

There are several supernova remnants that 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 of P≃75.3 ms and its derivative P{dot} ≃ 1.49x10^–13 s.s^–1. The corresponding characteristic parameters of the neutron star–age τ=P/2P{dot}=8.0 kyr, magnetic field B=3.4x10¹² G, and rotational energy loss E{dot}=1.4x10³⁷ ergs.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.