  The central source of the supernova remnant PKS 1209-52 was observed with the
Advanced CCD Imaging Spectrometer aboard Chandra X-ray observatory on 2000
January 6-7. The use of the Continuos Clocking mode allowed us to perform the
timing analysis of the data with time resolution of 2.85 ms and to find a
period P=0.42412927+/-2.3e-7 s. The detection of this short period proves that
the source is a neutron star. It may be either an active pulsar with
unfavorably directed radio beam or a truly radio-silent neutron star whose
X-ray pulsations are caused by a nonuniform distribution of surface
temperature. To infer the actual properties of this neutron star, the period
derivative should be measured.
