| We have conducted both targeted and wide-field surveys for exotic radio pulsars using the Arecibo, Green Bank, and Parkes telescopes. A survey of 22 globular clusters with Arecibo has discovered 11 millisecond pulsars, almost doubling the number known in these clusters. Ten of the new pulsars are in binaries, and 3 show eclipses. This survey has discovered significantly more very fast-spinning pulsars (Pspin ≲ 4 ms) and short orbital period systems (Porb ≲ 6 hr) than previous surveys of the same clusters. We discuss some characteristics of the globular cluster pulsar population in general, particularly the luminosity function.;Arecibo and Parkes searches of 5 potential ASCA X-ray counterparts to unidentified EGRET gamma-ray sources have revealed the young, energetic pulsar J2021+3651. PSR J2021+3651 is associated with the X-ray source AX J2021.1+3651, which in turn is likely associated with the COS B gamma-ray source 2CG 075+00, also known as GeV J2020+3658 and 3EG J2021+3716. This solves the long-standing mystery of this source's nature. Subsequent X-ray imaging and timing of PSR J2021+3651 with the Chandra observatory revealed a pulsar wind nebula whose morphology is reminiscent of the equatorial tori seen around some young pulsars, along with thermal emission from an embedded point source ( kTinfinity = 0.15+/-0.02keV). An observation in continuousclocking mode reveals a possible pulse detection from the point source.;Finally, we discuss two on-going, untargeted surveys of the Galactic Plane. These surveys hope to find exotic pulsars whose properties will elucidate the physics of pulsars, or which can potentially be used to study ultra-dense matter and strong gravity. The PALFA survey at Arecibo is using a 7-beam receiver at 1.4 GHz to cover the Arecibo-visible Galactic Plane. 28 pulsars have been discovered so far, including a few young, energetic pulsars and the youngest pulsar binary system known, PSR J1906+0746. The GBT350 survey at Green Bank is covering the Galactic Plane north of delta = 40°. Despite the 350-MHz observing frequency, the high resolution of these data allows us to maintain sensitivity to fast pulsars. Thus far, 14 pulsars have been discovered, 3 of which were found in time-domain searches for bright, dispersed bursts.;In observations of the rich, massive cluster Terzan 5 with the Green Bank Telescope we have discovered the 1.396-ms pulsar J1748--2446ad, which is now the fastest-spinning neutron star known. The difficulty in detecting this pulsar, due to its very low flux density and high eclipse fraction (∼40% of the orbit), suggests that even faster-spinning neutron stars exist. If the pulsar has a mass less than 2 M⊙ , then its non-rotating radius is constrained by the spin period to be < 16 km. The short period of this pulsar also constrains models that suggest gravitational radiation, through an r-mode instability, limits the maximum spin frequency of neutron stars. |
