Spectroscopy of a Balmer-dominated filament in the Cygnus Loop with the Hopkins Ultraviolet Telescope

摘要: A fair UV spectrum of a nonradiative filament in the Cygnus Loop covering wavelength range 830-1860 at 3.5-A resolution was obtained using Hopkins Ultraviolet Telescope (HUT) on Astro-1 space shuttle mission. Nonradiative shock models which include more sophisticated treatment Lyman line transfer are calculated. It is found that HUT can be explained terms with velocity 175-185 km/s propagating into low-density medium. This reconciled 135-km/s width broad component H-alpha this if equilibration postshock electron and ion temperatures proceeds much rapidly than Coulomb time scales. The required for 180-km/s to develop partial recombination zone short, about 200 yr n approximately equal 2/cu cm. suggests decelerating as it encounters denser material. current analysis patently favors rapid electrons ions behind shock.