Session 32. Supernova Remnants/ISM
Display, Thursday, November 9, 2000, 8:00am-6:00pm, Bora Bora Ballroom

## [32.15] Discovery of a 700 yr-old X-ray Pulsar in the SNR Kes~75

E.V. Gotthelf (Columbia), G. Vasisht (JPL/Caltech), K. Tori (NASDA), M. Boylan-Kolchin (Columbia)

We report the discovery of PSR~J1846-0258, a remarkable X-ray pulsar associated with the young supernova remnant Kes~75. We find a highly significant signal at a period of ~0.3 s with a broad, symmetric single pulse profile. From several archival RXTE and ASCA pointings of the region we are able to localize the source of the pulsations to Kes~75 and measure a period derivative of 7.1 \times 10-12 s/s. With a characteristic age of only 723 yr, consistent with the age of Kes~75, PSR~J1846-0258 is the youngest pulsar yet discovered. This pulsar is being spun down rapidly by torques from a large magnetic dipole of strength ~q 5\times 1013 G, just above the so-called quantum critical field BQED = m2ec3/e{\hbar}. PSR~J1846-0258 resides in this transitional regime where the magnetic field is hypothesized to separate the regular pulsars from the so-called magnetars. PSR~J1846-0258 is evidently a Crab-like pulsar, however, its period, spin-down rate, spin-down conversion efficiency, are each an order-of-magnitude greater, likely the result of its equally extreme magnetic field. Unlike its older cousin, the Crab, the Kes~73 system is one of those rare examples of a central plerion in a shell-type SNR; it provides strong evidence that neutron stars are born in supernovae explosions.

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\noindent The research is supported by NASA LTSA grant NAG5--7935.