GD 358

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GD 358
Observation data
Epoch J2000.0 (ICRS)
Constellation
(pronunciation)		 Hercules
Right ascension 16h 47m 19.02s[1]
Declination +32° 28′ 31.9″[1]
Apparent magnitude (V) 13.65[1]
Characteristics
Spectral type DBV2[2]
B-V color index -0.1[1]
Variable type DBV[2]
Astrometry
Proper motion (μ) RA: 6[1] mas/yr
Dec.: -162[1] mas/yr
Other designations
EGGR 239, V777 Her, V777 Herculis, PG 1645+325, WD 1645+325.

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 itself.[3] GD 358 was discovered during the 1958–1970 Lowell Observatory survey for high proper motion stars in the Northern Hemisphere.[4] 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.[5] Greenstein confirmed this in 1969.[6]

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.[7] 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.[8][9][10] In 1982, calculations by D. E. Winget and his coworkers suggested that helium-atmosphere DB white dwarfs with surface temperatures around 19,000 K should also pulsate.[11], p. L67. Winget then searched for such stars and found that GD 358 was a variable DB, or DBV, white dwarf.[12] This was the first prediction of a class of variable stars before their observation.[13], p. 89. In 1985, this star was given the variable-star designation V777 Her, which is also another name for this class of variable stars.[14]; [15], p. 3525

[edit] Notes and references

  1. ^ a b c d e f SIMBAD, accessed June 12, 2007.
  2. ^ a b A Catalog of Spectroscopically Identified White Dwarfs, George P. McCook and Edward M. Sion, Astrophysical Journal Supplement 121, #1 (March 1999), pp. 1–130. CDS ID III/210.
  3. ^ Asteroseismology of white dwarf stars, D. E. Winget, Journal of Physics: Condensed Matter 10, #49 (December 14, 1998), pp. 11247–11261. DOI 10.1088/0953-8984/10/49/014.
  4. ^ Lowell Proper Motion Survey: 8991 Stars with m > 8, PM > 0.26"/year in the Northern Hemisphere, H. L. Giclas, R. Burnham, Jr., N. G. Thomas, Flagstaff, AZ: Lowell Observatory, 1971. CDS ID I/79.
  5. ^ A list of white dwarf suspects II : special objects of small proper motion from the Lowell survey, Henry L. Giclas, Robert Burnham, and Norman Gene Thomas, Bulletin, Lowell Observatory, #141 (7, #4, 1967), pp. 49–54.
  6. ^ The Lowell Suspect White Dwarfs, Jesse L. Greenstein, Astrophysical Journal 158 (October 1969), pp. 281–293.
  7. ^ A New Short-Period Blue Variable, Arlo U. Landolt, Astrophysical Journal 153, #1 (July 1968), pp. 151–164.
  8. ^ Observations of variable white dwarfs: one new variable and 35 nonvariables, E. L. Robinson and J. T. McGraw, Astrophysical Journal 207 (July 1976), pp. L37–L40.
  9. ^ High-frequency stellar oscillations. XI. The ZZ Ceti star BPM 30551, J. E. Hesser, B. M. Lasker, and H. E. Neupert, Astrophysical Journal 209 (November 1976), pp. 853–857.
  10. ^ BPM 31594: a new southern-hemisphere variable white dwarf, J. T. McGraw, Astrophysical Journal 210 (November 1976), pp. L35–L38.
  11. ^ Hydrogen-driving and the blue edge of compositionally stratified ZZ Ceti star models, D. E. Winget, H. M. van Horn, M. Tassoul, G. Fontaine, C. J. Hansen, and B. W. Carroll, Astrophysical Journal 252 (January 15, 1982), pp. L65–L68.
  12. ^ Photometric observations of GD 358: DB white dwarfs do pulsate, D. E. Winget, E. L. Robinson, R. D. Nather, and G. Fontaine, Astrophysical Journal 262 (November 1, 1982), pp. L11–L15.
  13. ^ White Dwarf Stars, Steven D. Kawaler, in Stellar remnants, S. D. Kawaler, I. Novikov, and G. Srinivasan, edited by Georges Meynet and Daniel Schaerer, Berlin: Springer, 1997. Lecture notes for Saas-Fee advanced course number 25. ISBN 3540615202.
  14. ^ The 67th Name-List of Variable Stars, P. N. Kholopov, N. N. Samus, E. V. Kazarovets, and N. B. Perova, Information Bulletin on Variable Stars, #2681, March 8, 1985.
  15. ^ White dwarfs, Gilles Fontaine and François Wesemael, in Encyclopedia of Astronomy and Astrophysics, ed. Paul Murdin, Bristol and Philadelphia: Institute of Physics Publishing and London, New York and Tokyo: Nature Publishing Group, 2001. ISBN 0333750888.