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HFG1 (136+5°1) is a large, low-surface-brightness planetary nebula that was discovered by Heckathorn, Fesen, and Gull (Astrpn. Astronphys., 114, 414, 1982). in the autumn of 1986, photoelectric photometry by A.D.G. and H.E.B. showed that the 14th-mag central star of HFG1 is a large-amplitude variable. Subsequent CCD photometry by R.C. and H.E.B. reveals a sinusoidal variation with a period of 13.96 hr and an amplitude of 1.1 mag in the B band.
PG 1707+427 was identified in the Palomar-Green survey (Green Schmidt and Liebert, 1986) as an object with a significant ultraviolet excess. Observations by Bond and Grauer in 1982 showed it to be a pulsating variable (Bond, Grauer, Green and Liebert, 1984). Fourier transforms of the discovery time-series photometric runs revealed power in PG 1707+427’s light curves in two bands with periods near 450-s and 333-s. The longer period peak was observed to have a variable amplitude while the other one appeared relatively constant in strength. Wesemael, Green and Liebert (1985) placed PG 1707+427 in the spectroscopic class of PG 1159–035 (DOV) pulsating variables.
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