SIMBAD references

We present a timing study of the three known central compact object (CCO) pulsars, isolated cooling neutron stars in supernova remnants, using observations from Chandra, XMM-Newton, and NICER spanning two decades. Relative to canonical young pulsars, CCOs are spinning down at a very slow rate $| \dot{f}| \lt 1{0}^{-15}$ s^–2, implying a surface dipole magnetic field strength B_s < 10¹¹ G that is too weak to account for their X-ray-emitting hot spots. Two CCO pulsars with sufficiently long monitoring, 1E 1207.4-5209 and PSR J0821-4300, are seen to deviate from steady spin-down; their timing residuals can be modeled by one or more glitches in f and $\dot{f}$ or alternatively by extreme timing noise. For the third CCO pulsar, PSR J1852+0040, the sparse temporal coverage was insufficient to detect such effects. Glitch activity and timing noise in large samples of rotation-powered pulsars correlate best with $\dot{f}$, while the timing irregularities of the first two CCOs are extreme compared to pulsars of the same $\dot{f}$. Nevertheless, timing activity in CCOs may arise from properties that they share with other young but more energetic pulsars: high internal temperature, strong buried magnetic field, and superfluid behavior. Alternatively, continuing low-level accretion of supernova debris is not ruled out as a source of timing noise in CCOs.