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GD 358
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.〔(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.〕 GD 358 was discovered during the 1958–1970 Lowell Observatory survey for high proper motion stars in the Northern Hemisphere.〔(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 ).〕 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.〔(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.〕 Greenstein confirmed this in 1969.〔(The Lowell Suspect White Dwarfs ), Jesse L. Greenstein, ''Astrophysical Journal'' 158 (October 1969), pp. 281–293.〕
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.〔(A New Short-Period Blue Variable ), Arlo U. Landolt, ''Astrophysical Journal'' 153, #1 (July 1968), pp. 151–164.〕 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.〔(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.〕〔(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.〕〔(BPM 31594: a new southern-hemisphere variable white dwarf ), J. T. McGraw, ''Astrophysical Journal'' 210 (November 1976), pp. L35–L38.〕 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.〔(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.〕, p. L67. Winget then searched for such stars and found that GD 358 was a variable DB, or ''DBV'', white dwarf.〔(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.〕 This was the first prediction of a class of variable stars before their observation.〔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 3-540-61520-2.〕, 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.〔(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.〕; 〔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 0-333-75088-8.〕, p. 3525
==Notes and references==
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