<< < -ab ab- abo abs abs acc acc aco act ad add adj aeo afo agr Alf alg Alk Aln Alp alt amb ana anc ang ani ann Ant ant Ant apl apo app Aqu arc arg arr asc ass ast ast asy atm ato att aut aut axi > >>
An unexpected and undesirable event; an unforeseen and unplanned event or circumstance.
M.E., from M.Fr., from L. accidentum, pr.p. of accidere "to happen, fall out" from ad- "to" + cadere "to fall."
Došâmad, from doš- prefix meaning "bad, ill, abnormal" (Mid.Pers. duš-, duž-, O.Pers./Av. duš-, duž- "bad, ugly, evil," cognate with Skt. dus-, Gk. → dys- "bad, hard, unlucky") + âmad, from âmadan "to come, happen," as in the current term pišâmad "event, happening."
1) To welcome or salute with shouts or sounds of joy and approval; applaud.
anjâm dâdan (#)
Fr.: accomplir, exécuter
To bring to its goal or conclusion; carry out; perform; finish (Dictionary.com).
Anjâm dâdan, literally "to make an end of, to finish; to carry out," from anjâm "end, conclusion" (from Mid.Pers. hanjâm "end, completion, outcome;" ultimately from Proto-Ir. *ham-gam-, from *ham-, → com-, + *gam- "to come," cf. Av. gam- "to come," related to Pers. âmadan, → walk), + dâdan "to give, commit," → yield.
Fr.: œuvre accomplie, projet réalisé
1) An act or instance of carrying into effect; fulfillment.
M.E. a(c)ount(e), ac(c)ompte, from O.Fr. aco(u)nte, acont, "account, reckoning, terminal payment," from a "to," → ad- + cont "counting, reckoning of money to be paid," from L.L. computus "a calculation," from L. computare "calculate, → compute."
Ažmar, from Kurd. žmârtin, žmêr-, variant of šomâr, šomârdan "to → count."
To grow or increase gradually, by the process of → accretion.
Back-formation from → accretion.
Fr.: gaz accrété
The gas involved in various accretion processes, such as that fed into an → accretion disk, pulled by a compact object, or used in the mass growth of a galaxy.
accreting neutron star
setâre-ye notroni-ye farbâlandé
Fr.: étoile à neutron accrétrice
A → neutron star in a → binary system that accretes matter from the → campion star, either from the → stellar wind or from an → accretion disk that forms if the companion overflows its → Roche lobe. The → gravitational energy from the infalling matter provides at least part of the energy for the observed radiation and the accretion torques dominate the spin evolution. Despite these common properties, accreting → neutron stars display a wide variety of behaviors, depending on the neutron star → magnetic field strength, mass of the companion and properties of → accretion (A. K. Harding, 2013, Front. Phys. 8, 679).
Fr.: étoile accrétrice, étoile qui accrète
The star which → accretes matter, particularly in its protostellar phase or in a close binary system.
1) The process by which an object increases its mass under the influence of its
→ gravitational attraction.
Accretion plays a key role in a wide range of astrophysical phenomena.
In particular stars result from the accretion of material by a
→ protostar from a surrounding
→ molecular cloud.
The accumulation of mass on the protostar involves
the formation of an → accretion disk.
Theoretical and observational investigations of protostars and newborn stars
indicate the important role of → magnetic fields
in this process. They favor the magnetospheric accretion model for mass transfer
from the circumstellar disk onto the newborn star. In this model, the stellar magnetosphere
→ truncates the disk at a few stellar radii. Gas from the disk
accretes onto the star along the magnetic field lines and hits the stellar surface at
approximately the → free fall velocity, causing a strong accretion
shock. Various → emission lines, such as the hydrogen
→ Balmer series, He I 5876 Å, Brγ 2.17 μm,
and so forth are formed in the infalling magnetospheric flow. Moreover, optical/ultraviolet
excess continuum emission is produced in the → accretion shocks.
The accretion is accompanied
by mass ejection through collimated → bipolar jets.
L. accretionem (nom. accretio, gen. accretionis) "a growing larger," from stem of accrescere, from ad- "to" + crescere "to grow".
Farbâl from prefix → far- which conveys "increase, abundance" + bâl, from bâlidan "to grow, to wax great," Mid.Pers. vâlitan, Av. varəd-, varədait- "to increase, augment, strengthen, cause to prosper," Skt. vrdh-, vardhati.
Fr.: colonne d'accrétion
The channel through which matter is accreted onto a body such as a → protostar, → white dwarf, → neutron star, or → black hole. The accreting body possesses magnetic fields strong enough to disrupt the → accretion flow and carry the material through column-shaped channels directly on to a small fraction of the stellar surface near the magnetic poles.
Fr.: disque d'accrétion
A rotating disk of gas and dust formed around a center of strong gravity that pulls material off a surrounding or near-by gaseous object. Accretion disks are associated with several astrophysical objects such as → binary stars, → protostars, → white dwarfs, → neutron stars, and → black holes. Accretion disk forms because the infalling gas does not directly crash the accreting object due to its too high → angular momentum. The individual particles go into a circular orbit around the accretor because the circular orbit has the lowest energy for a given angular momentum. A spread in angular momentum values will give a population of particles moving on different orbits, so that a rotating disk of matter forms around the object. The matter in the disk becomes very hot due to internal friction and → viscosity as well as the tug of the accreting object. Since this hot gas is being accelerated it radiates energy and loses angular momentum and falls onto the accretor. Theoretical and observational pieces of evidence point to the importance of → magnetic fields in the accretion process. According to current models, the stellar magnetosphere → truncates the disk at a few stellar radii. Gas from the disk accretes onto the star along the magnetic field lines and hits the stellar surface at approximately the → free fall velocity, causing a strong accretion shock. See also → flared disk, → self-shadowed disk, → protoplanetary disk, → alpha disk model.
Fr.: flot d'accrétion
1) Flow of matter during an accretion process.
Fr.: taux d'accrétion
The amount of mass → accreted during unit time. The accretion rate for the → collapse of a singular → isothermal sphere is expressed by: dM/dt = 0.975 cs3/G, where cs is the isothermal → sound speed (Shu 1977, ApJ 214, 488). This relation can be written as: dM/dt = 4.36 x 10-6 (T / 20 K)3/2 in units of solar masses per year, where T is the temperature. Observed temperatures of 10-20 K in regions of → low-mass star formation imply accretion rates of about 10-6 to 10-5 solar masses per year. Accretion rates for → massive stars amount to values of 10-4 to 10-3 solar masses per year.
Fr.: choc d'accrétion
A → shock wave occurring at the surface of a compact object or dense region that is accreting matter with a → supersonic velocity from its environment. In the case of → young stellar objects the process is believed to take place by funneled streams in the form of → accretion columns that originate in the surrounding → accretion disk and flow along the → field lines of the → protostar → magnetosphere. The gas falls supersonically onto the surface of the central body and its impact produces strong shocks of a few million → kelvin, a phenomenon that is observable in → X-rays.
zamân-e farbâl, direš-e ~
Fr.: temps d'accrétion
To gather or collect, often in gradual degrees; heap up (Dictionary.com).
anbâré (#), âkumgar
A device for storing electricity. An electric current is passed between two plates in a liquid. This causes charges (due to electrolysis) in the plates and the liquid. Same as → secondary cell.
From L. accumulator, from accumulare "to heap up," from → ad- "in addition" + cumulare "heap up," from cumulus "heap."