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OVV Quasars
An optically violent variable quasar (often abbreviated as OVV quasar) is a type of highly variable quasar. It is a subtype of blazar that consists of a few rare, bright radio galaxies, whose visible light output can change by 50% in a day. OVV quasars have essentially become unified with highly polarized quasars (HPQ), core-dominated quasars (CDQ), and flat-spectrum radio quasars (FSRQ). Different terms are used, but the term FSRQ is gaining popularity, effectively making the other terms archaic. At visible wavelengths, they are similar in appearance to BL Lac objects but generally have stronger broad emission lines. Examples *3C 279 3C 279 (also known as 4C–05.55, NRAO 413, and PKS 1253–05) is an OVV quasar, optically violent variable quasar (OVV), which is known in the astronomical community for its variations in the Visible spectrum, visible, Radio frequency, radio and ... * S5 0014+81 References * * Active galaxy types {{quasar-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasar
A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous Accretion disk, accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosity, luminosities thousands of times greater than that of a galaxy such as the Milky Way. Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of Expansion of the universe, cosmological origin. The term originated as a Contraction (grammar), contraction of "quasi-stellar ''[star-like]'' radio source"—because they were first identified during the 1950s as sources of radio-wave ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blazar
A blazar is an active galactic nucleus (AGN) with a relativistic jet (a jet composed of ionized matter traveling at nearly the speed of light) directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away from Earth. Blazars are powerful sources of emission across the electromagnetic spectrum and are observed to be sources of high-energy gamma ray photons. Blazars are highly variable sources, often undergoing rapid and dramatic fluctuations in brightness on short timescales (hours to days). Some blazar jets appear to exhibit superluminal motion, another consequence of material in the jet traveling toward the observer at nearly the speed of light. The blazar category includes BL Lac objects and optically violently variable (OVV) quasars. The generally accepted theory is that BL Lac objects are intrinsically low-power radio galaxies while ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BL Lac Objects
A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization. Because of these properties, the prototype of the class (BL Lac) was originally thought to be a variable star. When compared to the more luminous active nuclei (quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range. This lack of spectral lines historically hindered identification of the nature and distance of such objects. In the unified scheme of radio-loud active galactic nuclei, the observed nuclear phenomenology of BL Lacs is interpreted as being due to the effects of the relativistic jet closely aligned to the line of sight of the observer. BL Lacs a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Emission Lines
A spectral line is a weaker or stronger region in an otherwise uniform and continuous spectrum. It may result from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to identify atoms and molecules. These "fingerprints" can be compared to the previously collected ones of atoms and molecules, and are thus used to identify the atomic and molecular components of stars and planets, which would otherwise be impossible. Types of line spectra Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nuclei) and a single photon. When a photon has about the right amount of energy (which is connected to its frequency) to allow a change in the energy state of the system (in the case of an atom this is usually an electron changing orbitals), the photon is absorbed. Then the energy will be spontaneously re-emitted, either as one photon at the same f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
3C 279
3C 279 (also known as 4C–05.55, NRAO 413, and PKS 1253–05) is an OVV quasar, optically violent variable quasar (OVV), which is known in the astronomical community for its variations in the Visible spectrum, visible, Radio frequency, radio and X-ray bands. The quasar was observed to have undergone a period of extreme activity from 1987 until 1991. The Rosemary Hill Observatory (RHO) started observing 3C 279 in 1971, the object was further observed by the Compton Gamma Ray Observatory in 1991, when it was unexpectedly discovered to be one of the brightest gamma ray objects in the sky. It is also one of the brightest and most variable sources in the gamma ray sky monitored by the Fermi Gamma-ray Space Telescope. It was used as a calibrator source for Event Horizon Telescope observations of M87* that resulted in the first image of a black hole. Observations * The apparent Superluminal#Astronomical observations, superluminal motion was detected during observations first made in 1973 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
S5 0014+81
S5 0014+81 is a distant, compact, hyperluminous, Spectral line, broad-absorption-line quasar, or blazar, located near the high declination region of the constellation Cepheus (constellation), Cepheus, near the North Equatorial Pole. Characteristics The object is an OVV quasar, OVV (optically violent variable) quasar, a type of blazar. It belongs to the most energetic subclass of Active galactic nucleus, active galactic nuclei, which are produced by the rapid accretion of matter by a central supermassive black hole, changing gravitational energy to light energy that can be visible across cosmic distances. In the case of S5 0014+81, it is one of the most luminous quasars known, with a total luminosity of over 1041 watts, equal to an absolute magnitude, absolute bolometric magnitude of −31.5. If the quasar were at a distance of 280 light-years from Earth, it would give out as much energy per square meter as the Sun does at Earth, despite being 18 million times more distant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
