1e 1207.4–5209: the Puzzling Pulsar at the Center of the Pks 1209–51/52 Supernova Remnant

Second Chandra observation of 1E 1207.4–5209, the central source of the supernova remnant PKS 1209–51/52, allowed us to confirm the previously detected period of 424 ms and, assuming a uniform spin-down, estimate the period derivative, Ṗ ∼ (0.7–3)× 10−14 s s−1. The corresponding characteristic age of the pulsar, P/2Ṗ ∼ 200– 900 kyr, is much larger than the estimated age of the SNR, ∼ 7 kyr. The values of the spin-down luminosity, Ė ∼ (0.4–1.6)×1034 erg s−1, and conventional magnetic field, B ∼ (2–4)×1012 G, are typical for a middle-aged radio pulsar, although no manifestations of pulsar activity have been observed. If 1E 1207.4–5209 is indeed the neutron star formed in the same supernova explosion that created PKS 1209–51/52, such a discrepancy in ages could be explained either by a long initial period, close to its current value, or, less likely, by a very large braking index of the pulsar. Alternatively, the pulsar could be a foreground object unrelated to the supernova remnant, but the probability of such a coincidence is very low. Subject headings: pulsars: individual (1E 1207.4–5209) — stars: neutron — supernovae: individual (PKS 1209–51/52) — X-rays: stars