Optical Imaging and Spectroscopy of the Galactic Supernova Remnants CTB 1 (G116.9+0.2), G116.5+1.1, and G114.3+0.3

Deep Hα , [N II], [S II], and [O III] Schmidt images of CTB 1 reveal substantially more emission than previous images of this galactic supernova remnant (SNR). A complete =~ 35' diameter shell is observed except for a large gap in the northeast with a morphology suggestive of a shell rupture. Faint Hα and [S II] filaments and diffuse Hα emission are detected as far as 30' eastward from the shell rupture point. These optical emissions, together with coincident x-ray emission extending eastward from the SNR interior, suggest that the CTB 1 shock has broken out into a large H I cavity off CTB 1's northeastern limb like that proposed by Fich [ApJ, 303, 465 (1986)]. CTB 1's optical morphology shows large variations when imaged in various emission lines. Particularly striking is the [O III]-bright western limb where spectra indicate relatively high [O III]/Hβ ratios (>= 25), implying shock velocities gtrsim 100 km s(-1) and large-scale, incomplete shock cooling possibly due to a strong interstellar magnetic field. Spectra taken along CTB 1's southeast and western rims indicate significant reddening variations, E(B-V) = 0.70\ to 1.0, consistent with the presence of several dust clouds visible around and in front of the SNR. Deep Hα and [S II] images of the neighboring SNR G116.5+1.1 reveal a 30' long filament along this remnant's NW rim, and spectra show [S II]/Hα = 1.02, confirming it as shock emission. An Hα image of a second nearby SNR, G114.3+0.3, shows several extremely faint filaments which may be associated with the SNR's radio-bright western limb.