THE BALMER-DOMINATED BOW SHOCK AND WIND NEBULA STRUCTURE OF γ-RAY PULSAR PSR J1741–2054

Abstract

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.