Proper motion and timing of two unusual pulsars: Calvera and 1E 1207.4-5209.
HALPERN J.P. and GOTTHELF E.V.
Abstract (from CDS):
Using pairs of images from the Chandra High Resolution Camera we examine the proper motion of the central compact object (CCO) 1E 1207.4-5209 in the supernova remnant (SNR) PKS 1209-51/52, and the unusual pulsar Calvera that is possibly a CCO descendant. For 1E 1207.4-5209, an insignificant proper motion of mas/yr is measured, corresponding to a corrected tangential velocity of km/s at the distance of 2 kpc. This proves that the previously noted large offset of the pulsar from the apparent geometric center of the SNR is not due to high proper motion; evidently the symmetry of the remnant does not indicate its center of expansion. Calvera has a marginally significant proper motion of mas/yr, corresponding to km/s for a hypothetical distance of 0.3 kpc. Notably, its vector is away from the Galactic plane, although its high Galactic latitude of may be more a consequence of its proximity than its velocity. We also provide updated timing solutions for each pulsar. Spanning 14.5 years, the ephemeris of 1E 1207.4-5209 has a small and steady frequency derivative that, because of the negligible proper motion, requires no kinematic correction. The derived surface dipole magnetic field strength of 1E 1207.4-5209 thus remains G. Calvera has G, intermediate between those of ordinary young pulsars and CCOs, suggesting that it may be on a trajectory of field growth that could account for the absence of descendants in the neighborhood of CCOs in the diagram.
pulsars: individual: (Calvera, 1E 1207.4-5209) - stars: neutron