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High-speed photometry reveals that the hot (≡100,000K) hydrogen-deficient white dwarf PG 0122+200 is a low-amplitude pulsating variable. The dominant periodicities are in the range 402 - 489 s, and appear to be due to nonradial g-modes. PG 0122+200 thus becomes the fifth known member of the PG 1159-035 (GW Vir) class, which includes three other PG white dwarfs and the central star of the planetary nebula K1-16.
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Bond et al. (1987) studied this question.
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