Nebular Lines in the Spectrum of AG Pegasi.

The discussion is based on 36 high-dispersion spectrograms taken between June, 1949, and September, 1956. During this interval the 800-day cycle in the displacements of emission lines continued, while resemblance to a typical symbiotic object increased. Numerous narrow bright lines of ionized metals exhibit changes in velocity of only 8 or 10 km/sec, while bright hydrogen lines vary through a range of 40 km/sec. The mean velocity from the hydrogen lines has decreased from +16 km/sec in 1915 to -27 km/sec in 1952. Shortward-displaced dark components of X 3888 of He I are still present. Velocities from M-type absorption lines vary through a small range. The velocity range of X 4363 of [0 iii] in the 800-day cycle is almost 70 km/sec, while that of X 5007, also of [0 iii] is less than 20 km/sec. The difference between the two lines is probably related to differences in density in various parts of the stellar system. The observed phenomena may arise from a jet of gas of relatively high density emitting chiefly X 4363, revolving near the center of the system and discharging into a large expanding outer zone which emits chiefly 5007.