The X-ray source 1E 1207.4 - 5209 is a compact central object in the G296.5+10.0 supernova remnant .
Its spin period of 424 ms , discovered with the Chandra X-ray Observatory , suggests that it is a neutron star .
The X-ray spectrum of this radio-quiet pulsar shows at least two absorption lines , first spectral features discovered in radiation from an isolated neutron star .
Here we report the results of timing analysis of Chandra and XMM -Newton observations of this source showing a non-monotonous behavior of its period .
We discuss three hypotheses which may explain the observational result .
The first one assumes that 1E 1207.4 - 5209 is a glitching pulsar , with frequency jumps of \Delta f \gtrsim 5 \mu Hz occurring every 1–2 years .
The second hypothesis explains the deviations from a steady spin-down as due to accretion , with accretion rate varying from \sim 10 ^ { 13 } 
to \gtrsim 10 ^ { 16 } g s ^ { -1 } , from a disk possibly formed from ejecta produced in the supernova explosion .
Finally , the period variations could be explained assuming that the pulsar is in a wide binary system with a long period , P _ { orb } \sim 0.2 –6 yr , and a low-mass companion , M _ { 2 } < 0.3 M _ { \odot } .