anomalous X-ray pulsar (AXP)
pulsâr-e pertwâ-ye iks-e nâsân
Fr.: pulsar X anormal
A member of a small class of → X-ray pulsars with long rotation periods (6-12 seconds), short → spin-down times (~ 103-105 years), and → soft X-ray spectrum. AXPs show no evidence of being → X-ray binary systems. Their magnetic fields, as deduced from their spin-down rate, are the highest known, reaching 1013-1015 → gauss. AXPs are generally believed to be → magnetars.
pulsâr-e dorin, tapâr-e ~
Fr.: pulsar binaire
A pulsar in a → binary system, the companion of which often being a → neutron star or a → white dwarf. The only known binary system with two pulsars components is the → double pulsar. As of 2010 about 70 binary pulsars have been identified. They are ideal laboratories for testing and studying the effects predicted by → general relativity, such as → spin precession, → Shapiro time delay, and → gravitational waves. The prototype, called PSR 1913+16, was discovered in 1974 by Russell A. Hulse and Joseph H. Taylor, Jr., who received the Nobel Prize for Physics in 1993. → Hulse-Taylor pulsar.
tapârhâ-ye siyâh-bivé, pulsârhâ-ye ~
A class of binary millisecond pulsars in which the pulsar is eclipsed by its stellar companion, and the companion is being gradually ablated by the relativistic wind of the pulsar. The first system discovered in 1988 was PSR 1957+20, a 1.6074 millisecond in a near circular 9 hr orbit around a low-mass companion star.
Black widow, a venomous spider (Latrodectus mactans), shiny, coal black in color, that lives in North and South America. The female averages 8-10 mm in length and has long slender legs and a round abdomen. → black; widow, from O..E. widewe, widuwe, from P.Gmc. *widewo (cf. Du. weduwe, weeuw, Ger. Witwe), from PIE *widhewo (cf. Av. viδavâ-, Mid.Pers. wêwag, Mod.Pers. bivé, Skt. vidhava-, L. vidua, Rus. vdova,); → pulsar.
pulsâr-e xarcang (#), tapâr-e ~ (#)
Fr.: pulsar du Crabe
pulsâr-e dotâyi, tapâr-e ~ (#)
Fr.: pulsar double
A → binary pulsar consisting of two pulsars. The only known example is PSR J0737-3039 (A and B), discovered in 2003 (Burgay et al. Nature 426, 531). The rotation periods of the pulsars are 22.7 and 2.8 milliseconds respectively. Each of them has a mass about 1.3 times that of the Sun and revolves around their → center of gravity with a period of 2.4 hours. According to the theory of → general relativity, such a binary should lose energy through the emission of → gravitational waves. As deduced from the change in orbital period, the separation of the pulsars is reducing by about 7 mm per day, in exact agreement with theory. It is expected that the pulsars will eventually merge in about 85 million years.
Hulse-Taylor pulsar (PSR 1913+16)
tapâr-e Hulse-Taylor, pulsâr-e ~
Fr.: pulsar de Hulse-Taylor
A → pulsar with a period of 59 milliseconds (17 pulses per second) moving around a compact companion in an elongated orbit (period 7.75 hours). It is thought that the companion is probably also a → neutron star with the same mass as the pulsar (1.4 solar masses). The orbit is gradually shrinking because of → gravitational radiation, as predicted by the theory of → general relativity. See also → binary pulsar, → millisecond pulsar.
Named after the American physicists Russell Hulse and Joseph Taylor of Princeton University, who discovered the pulsar in 1974, for which they shared the 1993 Nobel prize in physics; → pulsar.
pulsâr-e milisâniyé (#), tapâr-e ~ (#)
Fr.: pulsar milliseconde
A type of pulsar that spins around its axis every few thousands of a second. The prototype 1937+21, discovered in 1982, has a period of 1.56 milliseconds; i.e. it spins more than 600 times per second, the fastest so far found (Backer et al. 1982, Nature 300, 615). These pulsars are distinguished from typical pulsars by the extreme stability of their rotation period. It is thought that they have been rejuvenated by a "spin-up process" involving the accumulation of matter from a companion star. → recycled pulsar.
Fr.: pulsar à phase d'arrêt
pulsâr-e nuri, tapâr-e ~
Fr.: pulsar optique
pulsâr (#), tapâr (#)
A rotating → neutron star that emits a radio
→ beam that is centered on the
→ magnetic axis
of the neutron star. As the magnetic axis and hence the beam are inclined to the
→ rotation axis, a
→ pulse is seen every time the → rotation
brings the → magnetic pole
region of the neutron star into view. In this way the pulsar
acts much as a light house does, sweeping a beam of radiation through space.
The pulse or spin periods range from 1.4
milliseconds to 8.5 seconds. As neutron stars concentrate an average of 1.4
→ solar masses on a diameter of only 20 km, pulsars are
exceedingly → dense and → compact,
representing the densest matter in the observable Universe. The pulsar radiation,
chiefly emitted in → radio
frequencies (0.1-1 GHz), is highly
→ polarized. The exact mechanism by which a
pulsar radiates is still a matter of vigorous investigation.
Simply put, an enormous electric field is induced by the rotation of a
magnetized neutron star. The force of this field
exceeds gravity by ten to twelve orders of magnitudes.
Charged particles are whereby pulled out from the stellar surface
resulting in a dense, magnetized plasma that surrounds the pulsar
(→ magnetosphere). The charged particles flow out
of the magnetic → polar caps of the neutron star, following
magnetic field lines. The acceleration of the charged particles
along the curved magnetic field lines will cause them to radiate
(see, e.g., M. Kramer, 2010, astro-ph/1008.5032).
Pulsar, from puls(e) or puls(ing) + (st)ar.
geles-e pulsâr, ~ tapâr
Fr.: magnétosphère de pulsar
A dense zone of magnetized → plasma surrounding a → pulsar. The magnetosphere, lying between the surface of the → neutron star and the → light cylinder, corotates with the pulsar like a rigid body under the effect of strong magnetic field. The magnetosphere's thickness is determined by the constraint that the corotation velocity of its upper surface should not exceed the → speed of light.
Fr.: phase d'arrÃªt de pulsar
A phenomenon in which the → pulsar → emission abruptly drops to zero or near zero for a certain number of → pulse → periods, then suddenly returns to normal. Nulling is relatively common in pulsars. The → nulling fraction can be more than 80%. Investigating the emission behaviors of → nulling pulsars is important to understand the pulsar emission mechanism.
sayyâre-ye pulsâri, tapaar-e ~
Fr.: planète de pulsar
pulsar wind nebula (PWN)
miq-e bâd-e pulsâr, ~ ~ tapâr
Fr.: nébuleuse de vent de pulsar
Same as → plerion.
râdio-tapâr, pulsâr-e râdio-yi
Fr.: pulsar radio
A → pulsar that emits → pulses in → radio waves. The bulk of discovered pulsars are radio pulsars. There is a small number of pulsars that emit at optical wavelengths, X-ray wavelengths, and gamma-ray wavelengths.
pulsâr-e bâzcarx šodé
Fr.: pulsar recyclé
A → pulsar of abnormally low magnetic field and short period. The short period suggests that the pulasr is young, while the low field suggests a very old pulsar. According to theoretical models, a pulsar at some point in its evolution stops functioning as a pulsar. If it resides in a binary system (→ binary pulsar), its magnetic field decays in the interval when the companion evolves and fills its → Roche lobe. The dead pulsar is eventually spun up to life when → mass transfer from the companion begins. The pulsar gains → angular momentum from the infalling gas and increases its spin rate as more gas falls onto it. → Millisecond pulsars that spin hundreds of times per second are thought to be the result of such a transfer (see, e.g., G. Srinivasan, 2010, New Astronomy Reviews 54, 93, and references therein).
rotation-powered pulsar (RPP)
tapâr-e carxeš-tavân, pulsâr-e ~ ~
A → neutron star that is spinning down as a result of → torques from → magnetic dipole radiation and particle emission. RPPs derive their energy primarily from the → rotation of the neutron star. The energy from their → spin-down appears as broad-band pulsations from → radio to → gamma-ray wavelengths and as a → wind of energetic particles flowing into their surrounding → pulsar wind nebulae. Since the discovery of RPPs through their radio → pulsations in 1967, more than 2000 → radio pulsars are now known with periods ranging from a few milliseconds to several seconds (A. K. Harding, 2013, Front. Phys. 8, 679).
pulsâr-e Bâdbân, tapâr-e ~
Fr.: pulsar du Voile
A pulsar with a short period (89 milliseconds) associated with the → Vela supernova remnant. It is approximately 1500 light-years distant. The Vela pulsar is one of the few pulsars detectable optically. Its optical flashes, of visual magnitude 26, were detected in 1977. Also named PSR 0833-45.
pulsâr-e partowhâ-ye iks, tapâr-e ~ ~
Fr.: pulsar X
A regularly variable X-ray source in which the pulsation is associated with the rotation of a magnetized neutron star in an → X-ray binary. Periods range from a few seconds to a few minutes. Examples include Hercules X-1, Centaurus X-3, Cygnus X-3.