Abstract
We present the far-UV spectrum (900-1800 Å) of the bright filament known as Miller's (1974) position 1 in the Cygnus Loop obtained with the Hopkins Ultraviolet Telescope during the Astro-2 space shuttle mission. Longer wavelength IUE and ground-based spectra of adjoining regions were scaled to produce a combined spectrum ranging from 900 to 7500 Å. We compare this spectrum with models of radiative shock waves to infer shock velocities and elemental abundances. A power-law distribution of shock velocities within the spectrograph apertures can reproduce the observed spectrum. We consider the question of whether a simpler shock structure, thermally unstable cooling, or a mixing layer could produce a similar spectrum. We also discuss the elemental abundances with particular attention to C and Si, whose lines are only available in the UV.
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