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Post Common Envelope Binary
A post-common envelope binary (PCEB) or pre-cataclysmic variable is a binary system consisting of a white dwarf or hot subdwarf and a main-sequence star or a brown dwarf. The star or brown dwarf shared a common envelope with the white dwarf progenitor in the red giant phase. In this scenario the star or brown dwarf loses angular momentum as it orbits within the envelope, eventually leaving a main-sequence star and white dwarf in a short-period orbit. A PCEB will continue to lose angular momentum via magnetic braking (astronomy), magnetic braking and gravitational waves and will eventually begin mass-transfer, resulting in a Cataclysmic variable star, cataclysmic variable. While there are thousands of PCEBs known, there are only a few Eclipsing binaries, eclipsing PCEBs, also called ePCEBs. Even more rare are PCEBs with a brown dwarf as the secondary. A brown dwarf with a mass lower than 20 might Photoevaporation, evaporate during the common envelope phase and therefore the second ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 101584
HD 101584 is a suspected Post common envelope binary, post-common envelope binary about 1,800 to 5,900 light-years distant in the constellation of Centaurus. The system is bright at optical wavelengths with an apparent visual magnitude of about 7. The primary is either a Post-AGB Star, post-AGB star, but more likely a post-Red-giant branch, RGB star. The secondary is a red dwarf or possibly a low-luminosity white dwarf, which orbits the primary every 150-200 days. The system is surrounded by a slowly rotating Circumstellar disc#Binary system, circumbinary disk, probably with a face-on orientation towards the Solar System and a size of about 150 astronomical units. Variability In 1991, Jean Manfroid ''et al.'' published photometry (astronomy), photometry that showed that HD 101584 is a variable star. HD 101584 has been given the variable star designation V885 Centauri. The International Variable Star Index states that the star varies between visual magnitude 6.90 and 7. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detected in 1988, was confirmed in 2003. In 2016, it was recognized that the first possible evidence of an exoplanet had been noted in 1917. In collaboration with ground-based and other space-based observatories the James Webb Space Telescope (JWST) is expected to give more insight into exoplanet traits, such as their composition, environmental conditions, and potential for life. There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NN Serpentis
NN Serpentis (abbreviated NN Ser) is an eclipsing post-common envelope binary system approximately 1670 light-years away. The system comprises an eclipsing white dwarf and red dwarf. The two stars orbit each other every 0.13 days. Planetary system A planetary system has been inferred to exist around NN Ser by several teams. All of these teams rely on the fact that Earth sits in the same plane as the NN Serpentis binary star system, so humans can see the larger red dwarf eclipse the white dwarf every 0.13 days. Astronomers are then able to use these frequent eclipses to spot a pattern of small but significant irregularities in the orbit of stars, which could be attributed to the presence and gravitational influence of circumbinary planets. Chen (2009) used these "eclipse timing variations" to suggesting a putative orbital period spanning between 30 and 285 years and a minimum mass between 0.0043 and 0.18 Solar masses. In late 2009, Qian estimated a minimum mass of 10.7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HW Virginis
HW Virginis, abbreviated HW Vir, is an eclipsing binary system (of the Algol type), approximately 563 light-years away based on the parallax measured by the Gaia spacecraft, in the constellation of Virgo. The system comprises an eclipsing B-type subdwarf star and red dwarf star. The two stars orbit each other every 0.116795 days. Eclipse timing variations Based on variations in the timing of the system's eclipses, in 2008 it was claimed that two giant planets were in orbit around the binary, with masses of 8.47 and 19.2 times the mass of Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ... orbiting with periods of 9.1 and 15.8 years respectively. The proposed system was later shown to be extremely unstable, with mean lifetimes less than 1000 years in the para ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NSVS 14256825
NSVS 14256825, also known as V1828 Aquilae, is an eclipsing binary system (of the Algol type) in the constellation of Aquila. The system comprises a subdwarf O star and red dwarf star. The two stars orbit each other every 2.648976 hours. Based on the stellar parallax of the system, observed by ''Gaia'', the system is located approximately 2,700 light-years (840 parsecs) away. In 2007, Patrick Wils ''et al.'' discovered that NSVS 14256825 is an eclipsing binary, by examining the Northern Sky Variability Survey (NSVS) data. They also classified it as an HW Virginis type star, a binary pair in which variability arises from one star reflecting the light of the other as they orbit each other. Nomenclature The system is most commonly referred to using its designation from the NSVS, a survey of stars with apparent magnitudes between 8 and 15.5. It also has a variable star designation, V1828 Aquilae. Eclipse timing variations NSVS 14256825 has been extremely well-studie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NY Virginis
NY Virginis is a binary star about away. The primary belongs to the rare class of subdwarf B stars, being former red giants with their hydrogen envelope completely stripped by a stellar companion. The companion is a red dwarf star. The binary nature of NY Virginis was first identified in 1998, and the extremely short orbital period of , together with brightness variability on the timescale of 200 seconds was noticed, resulting in the identification of the primary star as a B-type subdwarf in 2003. Under a proposed classification scheme for hot subdwarfs it would be class sdB1VII:He1. This non-standard system indicates that it is a "normal" luminosity for a hot subdwarf and that the spectrum is dominated by hydrogen rather than helium. Planetary system In 2011, variations in the timing of the binary star's eclipses were used to infer the presence of a superjovian planet, NY Virginis (AB) b, on a wide orbit, with a second planet being suspected. A study in 2014 found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
White Dwarf
A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place in a white dwarf; what light it radiates is from its residual heat. 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 Jacob Luyten in 1922. White dwarfs are thought to be the final stellar evolution, evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the stars in the Milky Way. After the hydrogen-stellar nucleosynthesis, fusing period of a main sequence, main-sequence star of Stellar mass, lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumstellar Disc
A Circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form. Around mature stars, they indicate that planetesimal formation has taken place, and around white dwarfs, they indicate that planetary material survived the whole of stellar evolution. Such a disc can manifest itself in various ways. Young star According to the widely accepted model of star formation, sometimes referred to as the nebular hypothesis, a young star (protostar) is formed by the gravitational collapse of a pocket of matter within a giant molecular cloud. The infalling material possesses some amount of angular momentum, which results in the formation of a gaseous protoplanetary disc around the young, rotating star. The former is a rotating circumstellar disc of dense gas and d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SDSS 1557
SDSS 1557 (SDSS J155720.77+091624.6, WD 1554+094) is a binary star, binary system composed of a white dwarf and a brown dwarf. The system is surrounded by a Circumstellar disc#Binary system, circumbinary debris disk. The debris disk was formed when a minor planet was tidal force, tidally disrupted around the white dwarf in the past. The brown dwarf companion In 2011 it was found that the system did show Y- and J band (infrared), J-band excess, which hinted at a companion. Follow-up observations with instruments on the Gemini Observatory and the Very Large Telescope revealed the secondary, the brown dwarf SDSS 1557B, and a circumbinary disk around the binary. The researchers measured the radial velocity changes with the help of the Magnesium absorption line at 4482 angstrom, Å and found that a 66 brown dwarf orbits the white dwarf at around 0.7 , with the orbital period being around 2.27 hours. The irradiated brown dwarf also shows a hydrogen-alpha emission line. Add ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WD 0137−349
WD 0137-349 is a binary star in the constellation of Sculptor (constellation), Sculptor. It is located about 330 light-years (100 parsecs) away, and appears exceedingly faint with an apparent magnitude of 15.33. It is composed of a white dwarf with a brown dwarf in orbit around it, and is one of the few systems composed of a white dwarf and an associated brown dwarf. The brown dwarf orbits with a orbital period, period of 116 minutes, or nearly 2 hours. Properties The primary is a typical hydrogen white dwarf, as indicated by its spectral type of DA. It has about 39% of the Sun's mass and is only 1.86% as wide (12,900 km). With a high effective temperature of 16,500 Kelvin, K, it emits radiation mostly in the ultraviolet range. The brown dwarf, designated WD 0137-349B, can be detected from an infrared excess. Although it glows with an effective temperature of 1300 to 1400 K, the side facing the white dwarf's intercepts 1% of its light, and heats it up to around 2000 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
