  We have detected an Halpha bow shock nebula around PSR J1741-2054, a pulsar
discovered through its GeV gamma-ray pulsations. The pulsar is only ~1.5"
behind the leading edge of the shock. Optical spectroscopy shows that the
nebula is non-radiative, dominated by Balmer emission. The Halpha images and
spectra suggest that the pulsar wind momentum is equatorially concentrated and
implies a pulsar space velocity ~150km/s, directed 15+/-10deg out of the plane
of the sky. The complex Halpha profile indicates that different portions of the
post-shock flow dominate line emission as gas moves along the nebula and
provide an opportunity to study the structure of this unusual slow
non-radiative shock under a variety of conditions. CXO ACIS observations reveal
an X-ray PWN within this nebula, with a compact ~2.5" equatorial structure and
a trail extending several arcmin behind. Together these data support a close
(<0.5kpc) distance, a spin geometry viewed edge-on and highly efficient
gamma-ray production for this unusual, energetic pulsar.
