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 and gravitational waves and will eventually begin mass-transfer, resulting in a cataclysmic variable. While there are thousands of PCEBs known, there are only a few 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 evaporate during the common envelope phase and therefore the secondary is supposed to have a mass higher than 20 . The material ejected from the common envelop ...
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Eso2002a(1)
The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental research organisation made up of 16 member states for ground-based astronomy. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. The organisation employs about 730 staff members and receives annual member state contributions of approximately €162 million. Its observatories are located in northern Chile. ESO has built and operated some of the largest and most technologically advanced telescopes. These include the 3.6 m New Technology Telescope, an early pioneer in the use of active optics, and the Very Large Telescope (VLT), which consists of four individual 8.2 m telescopes and four smaller auxiliary telescopes which can all work together or separately. The Atacama Large Millimeter Array observes the universe in the millimetre and ...
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Eclipsing Binary
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called ''visual binaries''. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy (''spectroscopic binaries'') or astrometry (''astrometric binaries''). If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called ''eclipsing binaries'', or, together with other binaries that change brightness as they orbit, ''photometric binaries''. If components in binary star systems are close enough they can gravitationally distort their mutual outer stellar atmospheres. In some cases, these ...
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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 largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ... 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 p ...
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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 OB 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. Nomenclature The system is most commonly referred to using its designation from the Northern Sky Variability Survey (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-studied using photometry, but the resulting models often contradict each other, even with similar statistical significance, or with data that are collected later. Many studies have found that this system exhibits eclipse timing variations (ETVs) that are significant, cyclic and not e ...
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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 fo ...
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White Dwarf
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 the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is 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. White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way. After the hydrogen- fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant ...
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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 dus ...
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SDSS 1557
SDSS may refer to: * Sloan Digital Sky Survey, a major multi-filter imaging and spectroscopic redshift survey * Social Democratic Party of Slovakia * Spatial Decision Support System, a GIS based decision aiding system * Independent Democratic Serb Party, a political party of Croatian Serbs (''Samostalna demokratska srpska stranka'' in Serbo-Croatian) * South Delta Secondary School South Delta Secondary (SDSS) is a public high school in Tsawwassen, British Columbia, Canada. There are approximately 1,500 students enrolled in each grade 8 through 12 (as of 2019/2020). Graduation rates in the years 2005 to 2010 vary between 9 ...

CSS21055
Cascading Style Sheets (CSS) is a style sheet language used for describing the presentation of a document written in a markup language such as HTML or XML (including XML dialects such as SVG, MathML or XHTML). CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript. CSS is designed to enable the separation of content and presentation, including layout, colors, and fonts. This separation can improve content accessibility; provide more flexibility and control in the specification of presentation characteristics; enable multiple web pages to share formatting by specifying the relevant CSS in a separate .css file, which reduces complexity and repetition in the structural content; and enable the .css file to be cached to improve the page load speed between the pages that share the file and its formatting. Separation of formatting and content also makes it feasible to present the same markup page in different styles for different rendering metho ...
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WD 0137−349
WD 0137-349 is a binary star in the constellation of 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 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 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 K. The "night" side spectrum of WD 0137-349B ...
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SDSS J1205-0242
SDSS may refer to: * Sloan Digital Sky Survey, a major multi-filter imaging and spectroscopic redshift survey * Social Democratic Party of Slovakia * Spatial Decision Support System, a GIS based decision aiding system * Independent Democratic Serb Party, a political party of Croatian Serbs (''Samostalna demokratska srpska stranka'' in Serbo-Croatian) * South Delta Secondary School South Delta Secondary (SDSS) is a public high school in Tsawwassen, British Columbia, Canada. There are approximately 1,500 students enrolled in each grade 8 through 12 (as of 2019/2020). Graduation rates in the years 2005 to 2010 vary between 9 ...