Related Research Articles
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to Earth's. A white dwarf's low luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name white dwarf was coined by Willem Luyten in 1922.
BPM 37093 is a variable white dwarf star of the DAV, or ZZ Ceti, type, with a hydrogen atmosphere and an unusually high mass of approximately 1.1 times the Sun's. It is 48 light-years from Earth in the constellation Centaurus and vibrates; these pulsations cause its luminosity to vary. Like other white dwarfs, BPM 37093 is thought to be composed primarily of carbon and oxygen, which are created by thermonuclear fusion of helium nuclei in the triple-alpha process.
Gliese 570 is a quaternary star system approximately 19 light-years away. The primary star is an orange dwarf star. The other secondary stars are themselves a binary system, two red dwarfs that orbit the primary star. A brown dwarf has been confirmed to be orbiting in the system. In 1998, an extrasolar planet was thought to orbit the primary star, but it was discounted in 2000.
Giclas 29-38, also known as ZZ Piscium, is a variable white dwarf star of the DAV type, whose variability is due to large-amplitude, non-radial pulsations known as gravity waves. It was first reported to be variable by Shulov and Kopatskaya in 1974. DAV stars are like normal white dwarfs but have luminosity variations with amplitudes as high as 30%, arising from a superposition of vibrational modes with periods from 100 to 1,000 seconds. Large-amplitude DAVs generally differ from lower-amplitude DAVs by having lower temperatures, longer primary periodicities, and many peaks in their vibrational spectra with frequencies which are sums of other vibrational modes.
WD 0343+247 is a white dwarf in the ecliptic constellation of Taurus. It was discovered in 1997 when examination of photographs taken for a survey of brown dwarfs in the Pleiades revealed a faint star with high proper motion. It is one of the coolest white dwarfs known, with an effective temperature estimated to be approximately 3,800 K, equivalent to a spectral type of M0. Although referred to as WD 0346+246 in the discovery paper, it is more correctly designated WD 0346+247.
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. 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.
G117-B15A is a small, well-observed variable white dwarf star of the DAV, or ZZ Ceti, type in the constellation of Leo Minor.
LP 145-141, also known as LAWD 37, is an isolated white dwarf located 15.1 light-years from the Solar System in the constellation Musca. According to a 2009 paper, it is the fourth closest known white dwarf to the Sun
DENIS 0255−4700 is an extremely faint brown dwarf 15.9 light-years from the Solar System in the southern constellation of Eridanus. It is the closest isolated L-type brown dwarf, and only after the binary Luhman 16. It is also the faintest brown dwarf having measured visible magnitude. A number of nearer T and Y-type dwarfs are known, specifically WISE 0855−0714, Epsilon Indi B and C, SCR 1845-6357 B, and UGPS 0722−05.
WD 0806−661, formally named Maru, is a DQ white dwarf with an extremely cold Y-type substellar companion, located in the constellation Volans at 62.7 light-years from Earth. The companion was discovered in 2011, and is the only known Y-type companion to a star or stellar remnant. At the time of its discovery WD 0806-661 B had the largest actual and apparent separation of any known planetary-mass object, as well as being the coldest directly imaged substellar object then known.
Xi Pegasi is the Bayer designation for a double star in the northern constellation of Pegasus, the winged horse. Located in the horse's neck, the primary component is an F-type main sequence star that is visible to the naked eye with an apparent visual magnitude of 4.2. It is 86% larger and 17% more massive that the Sun, radiating 4.5 times the solar luminosity. Based upon parallax measurements taken with the Hipparcos spacecraft, it is located 53.2 ± 0.2 light years from the Sun.
Kelu-1 is a system of two brown dwarfs of spectral types L2 and L4 located in constellation Hydra at approximately 60.6 light-years from Earth. It is among the first free-floating later-than-M-type brown dwarfs discovered, and sometimes considered as prototype of L-type brown dwarfs.
DENIS-P J1228.2-1547 is a system of two nearly equal brown dwarfs, both are of spectral types L5.5:, located in constellation Corvus at approximately 20.2 parsecs or 66.0 light-years from Earth.
GD 165 is a system of a white dwarf and a brown dwarf of spectral types DA4 + L4, located in constellation Boötes at approximately 103 light-years from Earth. GD 165 B remained the only brown dwarf companion of a white dwarf until the discovery of GD 1400 B, which was discovered 17 years later.
CK Vulpeculae is an object whose exact nature is unknown. It was once considered to be the oldest reliably-documented nova. It consists of a compact central object surrounded by a bipolar nebula.
WD 1337+705 is a star in the constellation Ursa Minor. Shining with an apparent magnitude of 12.8, it is white dwarf 0.59 times as massive as the Sun. It is 86.5 light-years distant from Earth. It has 3% of the Sun's luminosity.
Ross 640 is a white dwarf star in the northern constellation of Hercules, positioned near the constellation border with Corona Borealis. With an apparent visual magnitude of 13.83, it is too faint to be visible to the naked eye. Its trigonometric parallax from the Gaia mission is 62.9″, corresponding to a distance of 52 light-years.
References
- 1 2 3 4 5 6 "Ruiz 439-26". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved October 22, 2020.
- 1 2 3 4 María Teresa Ruiz; P. Bergeron; S. K. Leggett; Claudio Anguita (1995). "The Extremely Low Luminosity White Dwarf ESO 439-26". The Astrophysical Journal. 455. Bibcode:1995ApJ...455L.159R. doi: 10.1086/309845 . S2CID 120193018.
- 1 2 3 4 5 6 7 Bergeron, P.; Leggett, S. K.; Ruiz, María Teresa (April 2001). "Photometric and Spectroscopic Analysis of Cool White Dwarfs with Trigonometric Parallax Measurements". Astrophysical Journal Supplement Series. 133 (2): 413–449. arXiv: astro-ph/0011286 . Bibcode:2001ApJS..133..413B. doi: 10.1086/320356 . S2CID 15511301.
- ↑ Ruiz, Maria Teresa; Bergeron, P.; Leggett, S. K.; Anguita, Claudio (1995-12-01). "The Extremely Low Luminosity White Dwarf ESO 439-26". The Astrophysical Journal. 455: L159. doi: 10.1086/309845 . ISSN 0004-637X.
- ↑ "The Faintest Known White Dwarf". www.noao.edu. 1 March 1996. Archived from the original on 12 March 2021. Retrieved 8 May 2020.
- ↑ Kaler, James B. (May 7, 2006). The Hundred Greatest Stars. Springer Science & Business Media. ISBN 9780387216256 – via Google Books.
 | This article about a white dwarf is a stub. You can help Wikipedia by expanding it. |