We analyze all X-ray timing data on 1E 1207.4 - 5209 in supernova remnant PKS 1209 - 51/52 gathered in 2000–2005 , and find a highly stable rotation with P = 424.130751 ( 4 ) ms and \dot { P } = ( 9.6 \pm 9.4 ) \times 10 ^ { -17 } s s ^ { -1 } .
This refutes previous claims of large timing irregularities in these data .
In the dipole spin-down formalism , the 2 \sigma upper limit on \dot { P } implies an energy loss rate \dot { E } < 1.5 \times 10 ^ { 32 } ergs s ^ { -1 } , surface magnetic field strength B _ { p } < 3.5 \times 10 ^ { 11 } G , and characteristic age \tau _ { c } \equiv P / 2 \dot { P } > 24 Myr .
This \tau _ { c } exceeds the remnant age by 3 orders of magnitude , requiring that the pulsar was born spinning at its present period .
The X-ray luminosity of 1E 1207.4 - 5209 , L _ { bol } \approx 2 \times 10 ^ { 33 } ( d / 2 { kpc } ) ^ { 2 } ergs s ^ { -1 } , exceeds its \dot { E } , implying that L _ { bol } derives from residual cooling , and perhaps partly from accretion of supernova debris .
The upper limit on B _ { p } is small enough to favor the electron cyclotron model for at least one of the prominent absorption lines in its soft X-ray spectrum .
This is the second demonstrable case of a pulsar born spinning slowly and with a weak B -field , after PSR J1852 + 0040 in Kesteven 79 .