Rino Bandiera: On the peculiar shapes of some pulsar bow-shock nebulae

Balmer lines, in particular Halpha are excellent tracers of bow-shock nebula. The "Guitar" nebula contains a fast moving pulsar moving toward the head of the Guitar. The field in X-rays contains a strange linear feature oriented about 120 degrees away from the pulsar's proper motion direction. The energetics of the pulsar spin-down does not seem to explain this elongated feature. He proposes the magnetic flux tubes of the ISM are directed along the direction of this feature. In this region, the gyration radius of electrons is comparable to the bow-shock size, and hence higher energy electrons would diffuse out the shock.