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[43.10] Detection of an HI shell at the rim of the Cygnus Loop

D.A. Leahy (U. Calgary), R.S. Roger (DRAO/HIA/National Research Council Canada)

21 cm neutral hydrogen line observations of the north-eastern part of the Cygnus Loop have been made with the Dominion Radio Astrophysical Observatory's Synthesis Telescope and the 26 m Telescope. Spectral line maps in 128 channels with 1.65 km s^-1 velocity separation were constructed for the region. Here we report the kinematic and positional evidence for a cloud of atomic material in the form of a expanding shell adjacent to the rim of the Cygnus Loop. The shell is of relatively high density (8cm^-3), is expanding at 20~km s^-1, is thick (~.9 pc ), has a mass ~10M_sun, and lies primarily on the far side of the Cygnus Loop. Possible origins of the shell are discussed.

This work supported in part by the Natural Sciences and Engineering Research Council of Canada.