GD 358 is a variable white dwarf star of the DBV type. Like other pulsating white dwarfs, its variability arises from non-radial gravity wave pulsations within the star itself.[8] GD 358 was discovered during the 1958–1970 Lowell Observatory survey for high proper motion stars in the Northern Hemisphere.[9] Although it did not have high proper motion, it was noticed that it was a very blue star, and hence might be a white dwarf.[10] Greenstein confirmed this in 1969.[11]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hercules |
| Right ascension | 16h 47m 19.02s[2] |
| Declination | +32° 28′ 31.9″[2] |
| Apparent magnitude (V) | 13.65[2] |
| Characteristics | |
| Spectral type | DBV2[3] |
| B−V color index | -0.1[2] |
| Variable type | DBV[3] |
| Astrometry | |
| Proper motion (μ) | RA: 6[2] mas/yr Dec.: -162[2] mas/yr |
| Parallax (π) | 23.2012 ± 0.0298 mas[4] |
| Distance | 140.6 ± 0.2 ly (43.10 ± 0.06 pc) |
| Absolute magnitude (MV) | +10.33[5] |
| Details | |
| Mass | 0.584[6] M☉ |
| Radius | 0.0110[7] R☉ |
| Luminosity | 0.0676[5] L☉ |
| Surface gravity (log g) | 7.92[7] cgs |
| Temperature | 24,937[7] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
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.[12] 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.[13][14][15] 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.[16], p. L67. Winget then searched for such stars and found that GD 358 was a variable DB, or DBV, white dwarf.[1] This was the first prediction of a class of variable stars before their observation.[17], 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.[18]; [19], p. 3525
Notes and references
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