An X-ray pulsar in the oxygen-rich supernova remnant G292.0+1.8

We report the discovery of pulsed X-ray emission from the compact object CXOU J112439.1-591620 within the supernova remnant G292.0+1.8 using the High Resolution Camera on the Chandra X-Ray Observatory. The X-ray period (P = 0.13530915 s) is consistent with the extrapolation of the radio pulse period of PSR J1124-5916 for a spin-down rate of (P) over dot = 7.6 x 10(-13) s s(-1). The X-ray pulse is single-peaked and broad, with an FWHM width of 0.23P (83degrees). The pulse-averaged X-ray spectral properties of the pulsar are well described by a featureless power-law model with an absorbing column density N-H = 3.1 x 10(21) cm(-2), a photon index Gamma = 1.6, and an unabsorbed 0.3-10 keV band luminosity L-x = 7.2 x 10(32) ergs s(-1). We plausibly identify the location of the pulsar's termination shock. Pressure balance between the pulsar wind nebula and the larger synchrotron nebula, as well as lifetime issues for the X-ray-emitting electrons, argue for a particle-dominated pulsar wind nebula that is far from the minimum-energy condition. Upper limits on the surface temperature of the neutron star are at, or slightly below, values expected from "standard" cooling curves. There is no optical counterpart to the new pulsar; its optical luminosity is at least a factor of 5 below that of the Crab pulsar.