Fr.: étoile à effet Blazhko
A star showing the → Blazhko effect.
blue halo star
setâregân-e âbi-ye hâlé
Fr.: étoiles bleues du halo
blue HB star
Fr.: étoile BHB
Same as → blue horizontal branch star.
blue hook star
setare-ye qollab-e abi
Fr.: étoile du crochet bleu
A rare class of → horizontal branch (HB)
stars that so far have been
found in only very few Galactic → globular clusters.
These stars are such called because they
form a blue hook at the hot end of the HB in
→ far ultraviolet
(FUV) → color-magnitude diagrams.
The physical mechanism that produces blue hook populations
is still uncertain. At least two scenarios have been proposed.
blue horizontal branch star
setâre-ye âbi-ye šâxe-ye ofoqi
Fr.: étoile bleue de la branche horizontale
A member of a population of blue stars appearing on the → horizontal branch in the → Hertzsprung-Russell diagram of the Galactic → halo populations and → globular clusters. Belonging to → spectral types B3 to A0, they have evolved past the → red giant stage and are burning helium in their core.
born-again AGB star
setâre-ye AGB-ye bâzzâdé
Fr.: étoile AGB recyclée
A → post-AGB star that undergoes a last → thermal pulse when it is already on the → white dwarf → cooling track. The thermal pulse will expand the hot central star, whereby hydrogen will be ingested into the → helium burning shell. This will temporarily return the star to the → AGB phase it has previously left.
Fr.: étoile Bq
burst of star formation
belk-e diseš-e setâregân
Fr.: flambée de formation d'étoiles
An intense → star formation activity in a region of → interstellar medium or, more globally, in a → galaxy. It is characterized by a → star formation rate which is much higher than the corresponding average. Same as → starburst.
Fr.: étoile B[e]
A → Be star with → forbidden lines in emission in its spectrum. B[e] stars show large → infrared excess due to → circumstellar dust emission. See also → supergiant B[e] star, → pre-main sequence B[e] star, → compact planetary nebula B[e] star, → symbiotic B[e] star, and → unclassified B[e] star.
B, referring to the spectral type; e for emission lines, brackets for distinction from Be; → star.
Fr.: étoile carbonée
carbon-enhanced metal-poor star (CEMP)
setâre-ye kamfelez-e karbon bolandidé
Fr.: étoile pauvre en métaux enrichie en carbon
A star that presents very low → iron → abundances [Fe/H] < -4 but an → anomalous richness in carbon. CEMP stars have been defined as a subset of → metal-poor stars that exhibit elevated [C/Fe] ≥ +1.0. It has been recognized that ~15-20% of stars with [Fe/H] < -2.0 are carbon enhanced. This fraction rises to 30% for [Fe/H] < -3.0, to 40% for [Fe/H] < -3.5, and ~75% for [Fe/H] < -4.0. This increasing trend of CEMP-star frequency with declining [Fe/H] is confirmed by the observation of many thousands of CEMP stars (Daniela Carollo + ApJ 2014, 788, 180). See also → extremely metal-poor star (EMPS)
setâre-ye pirâqotbi (#)
Fr.: étoile circumpolaire
Star that, from a given observer's → latitude, does not rise or set, but circles around the → celestial pole. To be circumpolar, a star must have a polar distance that is less than the observer's latitude. Whether a given star is circumpolar at the observer's latitude (φ) may be calculated in terms of the star's → declination (δ). The star is circumpolar if φ + δ ≥ +90° (observer in northern hemisphere), or φ + δ ≤ -90° (observer in southern hemisphere).
classical T Tauri star
setâre-ye T-Gâv-e kelâsik
Fr.: étoile T Tauri classique
A → T Tauri star in which → accretion from a → circumstellar disk is responsible for ultraviolet and infrared excess emission and for a moderate to strong emission line spectrum superimposed on the photospheric spectrum. Classical T Tauri stars probably evolve into → weak-line T Tauri stars when their disks are fully accreted by the stars.
close binary star
setâre-ye dorin-e kip
Fr.: étoile binaire serrée
A binary system in which the separation of the component stars is comparable to their diameters, so that they influence each other's evolution most commonly by the tidal forces.
Fr.: étoile CNO
Fr.: étoile dans son cocon
A star hidden in a dense envelope of gas and dust which is a strong source of infrared emission.
Fr.: étoile effondrée
A star that has undergone → collapse.
collective star formation
diseš-e gerdâmdi-ye setâregân
Fr.: formation collective d'étolies
Formation of stars, especially → massive stars, in group as opposed to individual formation.
compact binary star system
râžmân-e dorin-e hampak
Fr.: système binaire compact
A binary star system which is composed of a collapsed object
(→ degenerate dwarf, → neutron star,
or → black hole) in orbit with a low-mass (≤ 0.5 Msol)
secondary star, wherein the collapsed star → accretes
matter from its → companion.
These two objects form a binary system of overall dimensions
106 km with an orbital period of only hours or less.
→ X-ray binary.
compact planetary nebula B[e] star (cPNB[e])
setâre-ye B[e]-ye miq-e sayyâre-yi-ye hampak
Fr.: étoile de nébuleuse planétaire compacte