Pulsating white dwarf
White dwarf whose luminosity is variable / From Wikipedia, the free encyclopedia
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A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. Known types of pulsating white dwarfs include DAV, or ZZ Ceti, stars, with hydrogen-dominated atmospheres and the spectral type DA;[1] DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB;[2] and GW Vir stars, with atmospheres dominated by helium, carbon, and oxygen, and the spectral type PG 1159. (Some authors also include non-PG 1159 stars in the class of GW Vir stars.) GW Vir stars may be subdivided into DOV and PNNV stars;[3][4] they are not, strictly speaking, white dwarfs but pre-white dwarfs which have not yet reached the white dwarf region on the Hertzsprung-Russell diagram.[5][6] A subtype of DQV stars, with carbon-dominated atmospheres, has also been proposed,[7] and in May 2012, the first extremely low mass variable (ELMV) white dwarf was reported.[8]
These variables all exhibit small (1%–30%) variations in light output, arising from a superposition of vibrational modes with periods of hundreds to thousands of seconds. Observation of these variations gives asteroseismological evidence about the interiors of white dwarfs.[9]
Types of pulsating white dwarf[4][7][8][10] | |
DAV (GCVS: ZZA) | DA spectral type, having only hydrogen absorption lines in its spectrum |
DBV (GCVS: ZZB) | DB spectral type, having only helium absorption lines in its spectrum |
GW Vir (GCVS: ZZO) | Atmosphere mostly C, He and O; may be divided into DOV and PNNV stars |
DQV | DQ spectral type; hot, carbon-dominated atmosphere |
ELMV | DA spectral type; |