2004ApJ...601..479N

Chandra X-Ray Observatory imaging has shown that equatorial tori, often with polar jets, are very common in young pulsar wind nebulae (PWNe). These structures are interesting both for what they reveal about the relativistic wind itself and for the (nearly) model-independent measurement of the neutron star spin orientation they provide. The latter is a particularly valuable probe of pulsar emission models and neutron star physics. We describe here a procedure for fitting simple three-dimensional torus models to the X-ray data, which provides robust estimates of the geometric parameters. An application to six PWN tori gives orientations, PWN shock scales, and postshock wind speeds, along with statistical errors. We illustrate the use of these data by commenting on the implications for kick physics and high-energy beaming models.