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Be X-ray Binaries
Be/X-ray binaries (BeXRBs or BeXBs) are a class of high-mass X-ray binaries that consist of a Be star and a neutron star. The neutron star is usually in a wide highly elliptical orbit around the Be star. The Be stellar wind forms a disk confined to a plane often different from the orbital plane of the neutron star. When the neutron star passes through the Be disk, it accretes a large mass of hot gas in a short time. As the gas falls onto the neutron star, a bright flare in hard X-rays is seen. Definition and classification Be/X-ray binaries belong to the high-mass X-ray binary category. The optical companion is a non-supergiant, fast-rotating Be type star with emission lines indicating luminosity class III-V. Most BeXRBs have eccentric orbits and contain a neutron star, confirmed through X-ray pulsations. BeXRBs are classified as either transient or persistent. Transient BeXRBs show two outburst types: type I outbursts are regular, periodic events occurring near periastron (the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-mass X-ray Binaries
X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the ''donor'' (usually a relatively common main sequence star), to the other component, called the ''accretor'', which can be a white dwarf, neutron star or black hole. The infalling matter releases gravitational energy, gravitational potential energy, up to 30 percent of its rest mass, as X-rays. (Hydrogen nuclear fusion, fusion releases only about 0.7 percent of rest mass.) The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation. An estimated 1041 positrons escape per second from a typical X-ray binary#Low-mass X-ray binary, low-mass X-ray binary. Classification X-ray binaries are further subdivided into several (sometimes overlapping) subclasses, that perhaps reflect the underlying physics better. Not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Equivalent Width
The equivalent width of a spectral line is a measure of the area of the line on a plot of intensity versus wavelength in relation to underlying continuum level. It is found by forming a rectangle with a height equal to that of continuum emission, and finding the width such that the area of the rectangle is equal to the area in the spectral line. It is a measure of the strength of spectral features that is primarily used in astronomy. Definition Formally, the equivalent width is given by the equation W_\lambda = \int d\lambda = \int (1 - F_s / F_c) d\lambda. Here, F_c(\lambda) represents the underlying continuum intensity, while F_s(\lambda) represents the intensity of the actual spectrum (the line and continuum). Then W_\lambda represents the width of a hypothetical line which drops to an intensity of zero and has the "same integrated flux deficit from the continuum as the true one." This equation can be applied to either emission or absorption, but when applied to emission, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X Persei
X Persei is a high-mass X-ray binary system located in the constellation Perseus (constellation), Perseus, approximately 950 parsecs away. It is catalogued as 4U 0352+309 in the final Uhuru (satellite), Uhuru catalog of X-ray objects. The conventional star component of X Persei has been classified either as an O-type giant or a B-type main sequence star. It is a Be star, rotating rapidly, and at times surrounded by a disk of expelled material. This qualifies it as a Gamma Cassiopeiae variable, and the visual range is magnitude 6 - 7. In 1989 and 1990, the spectrum of X Persei changed from a Be star to a normal B class star while it faded significantly. This appears to have been caused by the loss of the excretion disk. The disk has since reformed and shows strong emission lines. The system also contains a neutron star which is a pulsar with an unusually long period of 837 seconds. The pulsar has shown period changes that are associated with mass transfer from the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
