GD 358

In 1968, Arlo U. Landolt discovered the first intrinsically variable white dwarf when he found that HL Tau 76 varied in brightness with a period of approximately 749.5 seconds, or 12.5 minutes. By the middle of the 1970s, a number of additional variable white dwarfs had been found, but, like HL Tau 76, they were all white dwarfs of spectral type DA, with hydrogen-dominated atmospheres. In 1982, calculations by Don Winget and his coworkers suggested that helium-atmosphere DB white dwarfs with surface temperatures around 19,000 K should also pulsate. Winget then searched for such stars and found that GD 358 was a variable DB, or DBV, white dwarf. This was the first prediction of a class of variable stars before their observation.^{, p. 89.} In 1985, this star was given the variable-star designation V777 Herculis, which is also another name for this class of variable stars.^;