Pulsating white dwarf
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; DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB; 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; 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. A subtype of DQV stars, with carbon-dominated atmospheres, has also been proposed, and in May 2012, the first extremely low mass variable (ELMV) white dwarf was reported.
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.
| Types of pulsating white dwarf | |
| 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; |
