We present the result of a Chandra ACIS observation of the pulsar PSR B1853+01 and its associated pulsar wind nebula ( PWN ) , embedded within the supernova remnant W44 .
A hard band ACIS map cleanly distinguishes the PWN from the thermal emission of W44 .
The nebula is extended in the north-south direction , with an extent about half that of the radio emission .
Morphological differences between the X-ray and radio images are apparent .
Spectral fitting reveals a clear difference in spectral index between the hard emission from PSR B1853+01 ( \Gamma \sim 1.4 ) and the extended nebula ( \Gamma \sim 2.2 ) .
The more accurate values for the X-ray flux and spectral index are used refine estimates for PWN parameters , including magnetic field strength , the average Lorentz factor \gamma of the particles in the wind , the magnetization parameter \sigma , and the ratio k of electrons to other particles .