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A kinematic and proper-motion survey of the Cygnus Loop
H-alpha radial velocities, line widths, and line intensities based on 71Fabry-Perot interferometer scans of 61 fields in the Cygnus Loopsupernova remnant SNR are reported. Also, measurements of proper motionsat 39 locations within the Cygnus Loop are summarized. These resultsshow that the remnant is expanding asymmetrically into the ambientinterstellar medium, with rest-frame velocities as high as 380 km/s inthe near half and 150 km/s in the far half. This can plausibly beinterpreted as the result of the progenitor's evolution near a densitydiscontinuity, the consequent formation of a cavity and partial shell,and the SN's interaction with that shell. The remnant's opticallyobserved filamentary structure results from line-of-sight effects asshock waves advance into the irregular inner surface of the shell. Inthis context, the derived expansion velocities and proper motions give aformal distance to the Cygnus Loop of roughly 600 pc, with 1-sigmalimits of 300 and 1200 pc.
| Meridian observations made in Brorfelde (Copenhagen University Observatory) 1975-76.
This catalogue presents positions for selected faint stars mainly fromAGK3 observed with the 7" transit circle at Brorfelde. The stars aredistributed in 43 selected areas around radio sources and are suitableas reference stars for measuring the optical counterparts to the radiosources. The obscr 'itioi cre carried out from 1975.16 to 1976.04, andevery star was observed at least two times giving a m.s.e. of "13 forthe catalogue positions given in the FK4 system. These positions usedtogether with AGK3 proper motions will in the period 1975 to 1980 have am.s.e. at the epoch ranging from `:13 to `:15, which is less than halfof what is expected when using AGK3 positions. Key words: transit circle- catalogue of positions
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