abar-now-axtar-e rombeš-e maqzé
Fr.: supernova à effondrement de coeur
delayed supernova explosion
oskaft-e bâderang-e abar-now-axtar
Fr.: explosion retardée de supernova
A mechanism predicted by theoretical models of → supernova explosion that operates after the → supernova shock fails to deliver a → prompt supernova explosion. The delayed supernova explosion mechanism assumes that a few tenth of a second after the → iron core collapse, the supernova shock is stalled due to energy dissipation. The material between the → protoneutron star and the stalled shock is mainly disintegrated into neutrons and protons due to the high temperatures (a few MeV) in this region. As the → neutrinos coming from the protoneutron star run through this material, a fraction of the neutrinos are captured by the → nucleons, and their energy is deposited in the material. As a result, the material behind the shock is heated by the neutrinos. If this neutrino heating is efficient enough, the stalled shock can be reinvigorated to bring about a supernova explosion.
novâ-ye kutulé, nowaxtar-e ~
Fr.: nova naine
A class of → novae and → cataclysmic variables that have multiple observed → eruptions. Their prototype is → U Geminorum star. Optically, dwarf nova eruptions have amplitudes of 2-6 mag in V, a duration of a few to 20 days and a recurrence time-scale of weeks to years. Dwarf novae are thought to be → semidetached binary stars consisting of a → white dwarf → primary accreting via → Roche lobe overflow from a → companion which is usually a → late-type, generally → main-sequence star. DN outbursts are usually attributed to the release of gravitational energy resulting from an → instability in the → accretion disk or by sudden mass transfers through the disk.
abar-now-axtar-e târixi (#)
Fr.: supernova historique
A supernova event recorded in the course of history before the invention of the telescope. The well recorded supernovae of this small group are SN 185, SN 1006, SN 1054 (→ Crab Nebula), SN 1181, SN 1572 (→ Tycho's star), and SN 1604 (→ Kepler's star).
A fast-evolving → supernova-like phenomenon resulting from the → merger of compact, binary objects such as two → neutron stars or a neutron star and a → black hole. A kilonova represents an → electromagnetic counterpart to → gravitational waves. Also called → macronova. A simple model of the phenomenon was put forward by Li and Paczynski (1998, ApJL 507, L59). The kilonova phenomenon can last between days and weeks following the merger. Within the small volume of space where a merger occurs, the combination of a huge amount of energy, and a large number of neutrons, is the instigator for the → r-process. The high density favors this rapid → neutron capture by nuclei, leading to the formation of new → chemical elements with high → atomic numbers and high → atomic weights. Many elements heavier than → iron form in these environments, including many rare elements, most notably → platinum (atomic number 78) and → gold (atomic number 79). The decay of heavy atomic nuclei leads to the radioactive heating and a release of electromagnetic radiation. The heat cannot easily escape as radiation, because of the high opacity of the ejected material. The heat is radiated thermally, heating up the nearby matter, which can be then seen in the → near-infrared. It was long thought that the r-process could also occur during core-collapse supernovae, but the density of neutrons within supernovae appears to be too low. The first indication of a kilonova following a short GRB came from the extensive follow-up of GRB 130603B, which was one of the nearest and brightest short GRBs ever detected, and also the first short GRB with an optical afterglow spectrum. The first kilonova found to be associated with a gravitational waves was detected in the study of → GW170817.
The term kilonova was introduced by Metzger et al. (2010, MNRAS 406, 2650), who argued that the peak luminosities of neutron star merger transients are typically ~ few × 1041 erg s-1, or a factor of ~ 103 larger than the → Eddington luminosity for a solar mass object. They therefore dubbed these events kilonovae; from → kilo-; → nova.
luminous red nova (LRN)
now-axtar-e sorx-e tâbân
Fr.: nova rouge lumineuse
A stellar explosion thought to be caused by the → merger of stars in a → binary system. They are characterized by a distinct red color, and a → light curve that lingers with resurgent brightness in the → infrared. The luminosity of the explosion is between that of a → supernova and a → nova.
A stellar → explosion with energies between those of a → nova and a → supernova and observationally distinguished by being brighter than a typical nova (MV ~ -8 mag) but fainter than a typical supernova (MV ~ -19 mag) (Kulkarni 2005; arXiv:astro-ph/0510256).
novâ, now-axtar (#)
abar-now-axtar-e nâpâydâri-ye joft
Fr.: supernova à instabilité de paires
A special type of → supernova that would result from the → pair instability in → supermassive stars with a mass range between 140 and 260 Msun in a low → metallicity environment. Such objects descended from the → Population III stars in the early history of the Universe. Such supernovae are the most powerful thermonuclear explosions in the Universe. Pair-instability supernovae may have played an important role in the synthesis of → heavy elements. Moreover, the energetic feedback of the processed elements to their surroundings could have affected the structure and evolution of the early Universe (See, e.g., Fryer et al. 2001, ApJ 550, 372; Heger & Woosley 2002, ApJ 567, 532). See also → pulsational pair-instability supernova.
The stage following a nova outburst, when the star has returned to a quiescent state.
Fr.: étape pré-nova
The stage of a star before its eruption to become a nova.
prompt supernova explosion
oskaft-e tond-e abar-now-axtar, ~ biderang-e ~
Fr.: explosion rapide de supernova
A mechanism predicted by theoretical models of → supernova explosion in the case when the → supernova shock breaks through the outer edge of the collapsing → iron core before losing all of its energy (through → photodisintegration of the iron nuclei) and manages to expel the stellar envelope. Compare with → delayed supernova explosion.
pulsational pair-instability supernova
abar-now-axtar-e nâpâydâri-ye tapeši-ye joft
Fr.: supernova à instabilité pulsationnelle de paires
A → supernova resulting from the → pair instability that generates several successive explosions. According to models, a first pulse ejects many solar masses of hydrogen layers as a shell. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs a few years later, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 1050 erg of light, about a factor of ten more than an ordinary → core-collapse supernova. After each pulse, the remaining core contracts, radiates neutrinos and light, and searches again for a stable burning state. Later ejections have lower mass, but have higher energy. They quickly catch up with the first shell, where the collision dissipates most of their kinetic energy as radiation. The first SNe from → Population III stars are likely due to pulsational pair instability (Woosley et al. 2007, Nature 450, 390). See also → pair-instability supernova.
Fr.: nova récurrente
Fr.: nova lente
A type of nova whose light curve exhibits a characteristically slow development, having a rise time of several days, maximum of several weeks, and slower decline.
Fr.: supernova superlumineuse
A → supernova with an → absolute magnitude of about -22 in optical. Examples of these newly discovered SNe include SN 2006gy, SN 2005ap, and SNe 2003ma. The nature of these objects is poorly known. Some of them are powered by the circumstellar interaction, or by the shock breakout from the dense circumstellar medium, as suggested by the presence of narrow emission lines in superluminous → Type II-N supernovae. It is also argued that superluminous SNe could be powered by a large amount of 56Ni which is synthesized as a result of energetic → core-collapse supernovae. Other scenarios include the interaction between shells ejected by the pulsational → pair-instability. See, e.g. Tanaka et al. 2012, MNRAS 422, 2675, arXiv:1202.3610, and references therein.
A violent stellar explosion which blows off all or most of the star's material at high velocity leaving a compact stellar remnant such as a → neutron star or → black hole. At → maximum light, the supernova can have → luminosity about 108 or 109 times the → solar luminosity. The phenomenon results from the later evolution of stars when an instability sets in the core following the → nucleosynthesis of → iron. In → massive stars, the supernova occurs when the star has used up all its available → nuclear fuel and it reaches a lower energy state through → gravitational collapse to form a more compact object. In → white dwarfs forming → binary systems, → accretion of mass onto the surface of a neutron star can be sufficient to take the star over the upper mass limit for stability as a white dwarf. Consequently, the white dwarf collapses in a → supernova explosion to form a neutron star. There are several → supernova types.
Fr.: candidat supernova
A star which according to observational data could become a supernova.
Fr.: éjecta de supernova
The material ejected by a → supernova explosion.