Ap and Bp stars are chemically peculiar stars (hence the "p") of types A and B which show overabundances of some metals, such as strontium, chromium and europium. In addition, larger overabundances are often seen in praseodymium and neodymium. These stars have a much slower rotation than normal for A and B-type stars, although some exhibit rotation velocities up to about 100 kilometers per second.
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The spatial locations of the chemical overabundances have been shown to be connected with the geometry of the magnetic field. Some of these stars have shown radial velocity variations arising from pulsations of a few minutes. For studying these stars high- resolution spectroscopy is used, together with Doppler imaging which uses the rotation to deduce a map of the stellar surface. These patches of overabundances are often referred to as abundance spots.
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The primary, component A, has a stellar classification of B8 IIIp, suggesting it is a B-type giant star. It a mercury-manganese star, a type of chemically peculiar star showing large overabundances of those two elements in the outer atmosphere. It is classified as an Alpha2 Canum Venaticorum type variable star and its brightness varies from magnitude +5.22 to +5.27 with a period of 5 days.
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This is a single-lined spectroscopic binary star system with an orbital period of 15.8 days and an eccentricity of 0.31. The primary member, component A, is an A-type main sequence star with a stellar classification of A1VsSi:. The stellar spectrum has the appearance of a hot Am star, showing overabundances of many iron-peak and heavier elements, but an underabundance of helium. In particular, it has an abnormal abundance of silicon.
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Its atmosphere has overabundances of some elements, such as silicon, mercury, and europium. This is thought to be due to some elements sinking down into the star under the force of gravity while others are elevated by radiation pressure. This star is the prototype of a class of variable stars, the so- called α2 Canum Venaticorum variables. The strong magnetic field of these stars is believed to produce starspots of enormous extent.
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It belongs to the class of chemically peculiar stars known as a Mercury-Manganese star, showing overabundances of mercury, manganese, and silicon in its spectrum. It is a suspected α2 CVn variable with magnitude variation from 4.35 to 4.39. The star has nearly three times the mass of the Sun and double the Sun's radius. It is radiating 81 times the Sun's luminosity from its photosphere at an effective temperature of 12,110 K.
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In Greece, bloodletting was in use in the fifth century BC during the lifetime of Hippocrates, who mentions this practice but generally relied on dietary techniques. Erasistratus, however, theorized that many diseases were caused by plethoras, or overabundances, in the blood and advised that these plethoras be treated, initially, by exercise, sweating, reduced food intake, and vomiting. Herophilus advocated bloodletting. Archagathus, one of the first Greek physicians to practice in Rome, also believed in the value of bloodletting.
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The star made its closest approach to the Sun some 8.7 million years ago at a separation of around . Roughly 40 million years old, this is an evolved K-type giant star with a stellar classification of . The suffix notation indicates overabundances of calcium and the cyanide molecule have been found in the spectrum of the stellar atmosphere. The star has 7.4 times the mass of the Sun and has expanded to 28 times the Sun's radius.
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It is moving closer with a heliocentric radial velocity of −11 km/s. This is a magnetic CP star with a stellar classification of , indicating this is an A-type main-sequence star. The spectrum has very weak lines of helium but displays strong overabundances of silicon and all of the heavier elements except nickel. It is classified as an Alpha² Canum Venaticorum variable with a magnitude that varies from 6.33 to 6.41 over a period of 2.88756 days.
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Zeta Capricorni, Latinized from ζ Capricorni, is a fourth-magnitude star in the constellation Capricornus. ζ Capricorni is a binary star, with the primary component ζ Capricorni A being a yellow G-type giant with an apparent magnitude of +3.77. It is considered one of the prototypical examples of a Barium star, properties of which include overabundances of carbon molecules (such as C2) and s-process elements. Zeta Capricorni has an overabundance of the s-process element praseodymium.
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It is a suspected eclipsing binary with a variable star designation V983 Centauri. The brighter member, designated component A, is a magnitude 4.52 chemically peculiar star of the helium-weak (CP4) variety, and has a stellar classification of B5 III-IVp. The spectrum of the star displays overabundances of elements such as nitrogen, phosphorus, manganese, iron, and nickel, while carbon, oxygen, magnesium, aluminium, sulfur, and chlorine appear underabundant relative to the Sun. Weak emission line features are also visible.
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It is a chemically peculiar star of the HgMn type, with a spectrum that displays anomalous overabundances of mercury, manganese, and silicon. This component is most likely a single-lined spectroscopic binary with an unknown companion. Its magnitude 5.76 visible companion, π2 Boötis, is a white-hued A-type main-sequence star with a class of A6 V. As of 2010, the pair were separated by arcseconds on the sky along a position angle of . This corresponds to a projected separation of .
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This is an evolved K-type giant star with a stellar classification of , showing overabundances of CN and CH molecules in the spectrum. It is a red clump giant, which indicates is on the horizontal branch generating energy via helium fusion at its core. The star is about 288 million years old with 3.5 times the mass of the Sun and 15 times the Sun's radius. It is radiating 87 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,909 K.
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It displays a mild overabundance of the element barium, which is hypothesized to have been accreted when an unresolved white dwarf companion was passing through the asymptotic giant branch (RGB) stage. The visible component displays significant overabundances of three s-process peak elements that are generated during the RGB phase, as well as a mild overabundance of carbon. In contrast, it shows severe depletion of lithium and beryllium, as well as a notable underabundance of boron. The surface abundances of these lighter elements may have been altered during the mass transfer process, having been previously consumed in the core region of the companion.
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Because technetium is radioactive, with a half-life much less than the age of the star, its abundance must reflect its recent creation within that star. Equally convincing evidence of the stellar origin of heavy elements is the large overabundances of specific stable elements found in stellar atmospheres of asymptotic giant branch stars. Observation of barium abundances some 20–50 times greater than found in unevolved stars is evidence of the operation of the s-process within such stars. Many modern proofs of stellar nucleosynthesis are provided by the isotopic compositions of stardust, solid grains that have condensed from the gases of individual stars and which have been extracted from meteorites.
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49 Camelopardalis is a variable star in the northern circumpolar constellation of Camelopardalis, located 313 light years from the Sun based on parallax measurements. It has the variable star designation BC Camelopardalis; 49 Camelopardalis is the Flamsteed designation. This star is a challenge to view with the naked eye, having a baseline apparent visual magnitude of 6.50. It is moving away from the Earth with a heliocentric radial velocity of +6.5 km/s. This is a magnetic chemically peculiar star with a stellar classification of A7VpSrCrEuSiKsn, indicating it is an A-type main-sequence star with overabundances of various elements including strontium and europium, as well as broad, "nebulous" lines.
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The primary component is a B-type main-sequence star with a stellar classification of B8/9V. Garrison and Gray (1994) assigned it a class of , displaying the calcium K line of a B8 class star, the hydrogen lines of a B9 star, and the helium lines of an A0 star, along with overabundances of strontium and iron. It is around 57 million years old with three times the mass of the Sun and about 2.1 times the Sun's radius. It is radiating 60.5 times the luminosity of the Sun from its photosphere at an effective temperature of 10,592 K. The star is spinning with a projected rotational velocity of 48 km/s.
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The stellar classification of this star is B9 IV:HgMn, although the ':' indicates an uncertain spectral value. The luminosity class of IV indicates that this is a subgiant that has exhausted the hydrogen at its core and it is in the process of evolving into a giant star. At present it has about 3.4 times the Sun's radius, 3.45 times the mass of the Sun, and is radiating 251 times the Sun's luminosity from its photosphere at an effective temperature of 12,800 K. Mu Leporis is a suspected Alpha² Canum Venaticorum variable with a period of about two days, although this has not been confirmed. The stellar spectrum of this star shows overabundances of mercury and manganese, as indicated by the HgMn in the stellar class.
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The elements heavier than iron with origins in dying low-mass stars are typically those produced by the s-process, which is characterized by slow neutron diffusion and capture over long periods in such stars A calculable model for creating the heavy isotopes from iron seed nuclei in a time- dependent manner was not provided until 1961. That work showed that the large overabundances of barium observed by astronomers in certain red-giant stars could be created from iron seed nuclei if the total neutron flux (number of neutrons per unit area) was appropriate. It also showed that no one single value for neutron flux could account for the observed s-process abundances, but that a wide range is required. The numbers of iron seed nuclei that were exposed to a given flux must decrease as the flux becomes stronger.
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Their study was called a "major contribution" in providing data to help identify the relatively rare Population II stars. It created an unbiased sample, and doubled the number of known peculiar A-type (Ap) stars. After nineteen years of study by various investigators, in 2014, Beers et al. studied 302 of the Bidelman-MacConnell possible weak-metal stars and concluded that a metal-weak thick disk (MWTD) is present in the Milky Way galaxy, and noted its importance in understanding the development of our galaxy. In 1962 and 1966, Bidelman had reported that the wavelength of λ 3984 varied somewhat from star to star, and stated differences in the ratios of mercury isotopes could be the reason. Bidelman was the first to note this, and in 1974, Michaud, Reeves and Charland, considering the isotopic abundances to be real, and that Hg was in fact overabundant and not an artifact of blending, suggested the mercury overabundances were due to radiation pressure that caused the element to pile up until radiation and gravitational forces almost cancelled each other, then its isotopes would separate, sorting themselves. Michaud suggested that element segregation would proceed naturally due to gravitational settling and radiation pressure if the stellar atmosphere was steady.
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