[Previous] | [Session 41] | [Next]
G. Vasisht (JPL/Caltech), E. V. Gotthelf (Columbia U.), T. Dotani (ISAS-Japan)
We present the spin-down history of the recently discovered 12-s pulsar in Kes 73, 1E~1841-045 using new ASCA observations and archival GINGA and ROSAT measurements. We confirm the remarkably rapid but steady spin-down rate for this pulsar of 4.1 \times 10-11 s/s, orders of magnitude faster than the Crab-like pulsars. Most importantly, the characteristic pulsar age is consistent with the age derived for the host SNR (~2,000 yrs). The ASCA flux has remained steady and consistent with the Rosat flux measurement. The ASCA spectrum also remains unchanged, described by a steep power-law of photon index ~3.4, most unlike a typical Crab-like or recycled pulsar.
The unusual spectral and temporal properties of 1E~1841-045 are similar to the other seemingly isolated, young anomalous X-ray pulsars; and these objects appear related to the SGRs. As an ``isolated'' NS, this pulsar is the one having the longest spin period ever observed. If these and other NS candidates like them were indeed born as fast rotators, then a mechanism must be found to slow them down to their currently observed rates. The rapid but steady spin-down of the Kes~73 pulsar suggests a possibility. The equivalent magnetic field for a rotating dipole is Bdipole ~q 3.2\times1019~(P\dot P)1/2 \approx 8\times 1014 G, one of the highest magnetic fields observed in nature. We suggest that the pulsar in Kes~73 was born as such a ``magnetar'' ~2,000 yrs ago and has since spun down to a long period due to rapid dipole radiation losses; 1E~1841-045 provides the first direct evidence of a magnetar and suggests an alternative evolutionary path for young pulsars.