Discovery of an Ultra-fast X-ray Pulsar in the Supernova Remnant N157B

We present the serendipitous discovery of 16 ms pulsed X-ray emission from the Crab-like supernova remnant N157B in the Large Magellanic Cloud. This is the fastest spinning pulsar associated with a supernova remnant (SNR). Observations with the Rossi X-ray Timing Explorer (RXTE), centered on the field containing SN1987A, reveal an X-ray pulsar with a narrow pulse profile. Archival ASCA X-ray data confirm this detection and locate the pulsar within 1 of the supernova remnant N157B, 14 from SN1987A. The pulsar manifests evidence for glitch(es) between the RXTE and ASCA observations which span 3.5 years; the mean linear spin-down rate is Ṗ = 5.126 × 10 s s. The background subtracted pulsed emission is similar to other Crab-like pulsars with a power law of photon index of ∼ 1.6. The characteristic spin-down age (∼ 5000 years) is consistent with the previous age estimate of the SNR. The inferred B-field for a rotationally powered pulsar is ∼ 1× 10 Gauss. Our result confirms the Crab-like nature of N157B; the pulsar is likely associated with a compact X-ray source revealed by ROSAT HRI observations. Subject headings: pulsars: general — pulsars: individual (PSR J0537−6910) — X-rays: general — supernova remnant Laboratory for High Energy Astrophysics, NASA/GSFC, Greenbelt, MD 20771; [email protected], [email protected], [email protected] Universities Space Research Association Los Alamos National Laboratory, MS B265, CIC-19, Los Alamos, NM 87545; [email protected] Dearborn Observatory, Northwestern University, 2131 Sheridan Road, Evanston, IL 60208; [email protected]