Showing papers by "William T. Reach published in 1990"

Detection of an expanding H I shell in the old supernova remnant CTB 80

Abstract: An expanding H I shell associated with the SNR CTB 80 has been detected. The expansion velocity and size indicate that the H I shell is an SNR shell. The center, shape, and mass of the shell match those of the IR shell detected by Fesen et al. (1988), supporting the idea that the pulsar has caught up with the SW portion of the shell and has produced its peculiar radio morphology. The shell's large 60 to 100 micron ratio implies that the larger grains may have been preferentially destroyed by the shock.

A Large Bubble around the Crab Nebula

Abstract: IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.