Alpha Coronae Borealis

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Alpha Coronae Borealis
Template:Location mark
Location of α Coronae Borealis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.24[2]
Characteristics
Spectral type A0V + G5V[3]
U−B Template:Engvar −0.03[4]
B−V Template:Engvar −0.02[4]
Variable type Eclipsing binary[5]
Astrometry
Radial velocity (Rv)+1.7[6] km/s
Proper motion (μ) RA: 120.27[1] mas/yr
Dec.: −89.58[1] mas/yr
Parallax (π)43.46±0.28 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)+0.16/+5.05[3]
Orbit[7]
Period (P)17.3599 d[8]
Semi-major axis (a)Script error: No such module "val".
Eccentricity (e)Script error: No such module "val".
Inclination (i)88.2°
Periastron epoch (T)Script error: No such module "val". (JD)
Argument of periastron (ω)
(secondary)		Script error: No such module "val".°
Semi-amplitude (K1)
(primary)		Script error: No such module "val". km/s
Semi-amplitude (K2)
(secondary)		Script error: No such module "val". km/s
Details[9]
α CrB A
MassScript error: No such module "val". Template:Solar mass
RadiusScript error: No such module "val". Template:Solar radius
Luminosity74 Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val". cgs
TemperatureScript error: No such module "val". K
Rotational velocity (v sin i)139[10] km/s
Age400[7] Myr
α CrB B
MassScript error: No such module "val". Template:Solar mass
RadiusScript error: No such module "val". Template:Solar radius
Luminosity0.83 Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val". cgs
TemperatureScript error: No such module "val". K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Rotational velocity (v sin i)< 14[8] km/s
Other designations
Gemma, Alphecca, Ashtaroth, Gnosia Stella Coronae, 5 CrB, BD+27°2512, GCTP 3519.00, FK5 578, HD 139006, HIP 76267, HR 5793, SAO 83893.
Database references
SIMBADdata

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Alpha Coronae Borealis (α Coronae Borealis, abbreviated Alpha CrB, α CrB), officially named Alphecca Template:IPAc-en,[11] is an eclipsing binary star in the constellation of Corona Borealis. It is located about 75 light years from the Sun and contains two main sequence stars, one class A and one class G.

Properties

File:AlphaCrBLightCurve.png
A light curve for Alpha Coronae Borealis, plotted from TESS data[12]
File:Alpha Coronae Borealis.jpg
α Coronae Borealis in optical light

Alpha Coronae Borealis is a binary system, its stars orbiting each other in an eccentric orbit every 17.36 days. Because the plane of this orbit is inclined at an angle of 88.2° to the line of sight to the Earth,[8] the pair form a detached eclipsing binary system similar to Algol (β Per). The periodic eclipses result in a magnitude variation of +2.21 to +2.32, which is hardly noticeable to the unaided eye.

The primary component is a white main sequence star that has a stellar classification of A0V and 2.6 times the mass of the Sun. Estimates of the star's radius range from 2.89 to 3.04 times the radius of the Sun.[3][8] An excess of infrared radiation at 24 μm and 70 μm has been detected about the primary star by the IRAS.[13] This suggests the presence of a large disc of dust and material around the star, prompting speculation of a planetary or proto-planetary system similar to that currently assumed around Vega. The disk extends out to a radius of around 60 astronomical units (AU).[14]

The secondary component is a yellow main sequence star with an estimated stellar class of G5, 0.92 times the Sun's mass and 0.90 times the Sun's radius. The X-ray luminosity of this star is 6 × 1028 erg s−1, which is 30 times greater than the peak activity level of the Sun. This higher activity level is expected for a young star of this class. The corona has a temperature of about 5 MK, which is much hotter than the Sun's corona. The upper limit of 14 km/s for the equatorial rotation velocity is equivalent to a rotation period of 3 days. More likely, the rotation period is 7–9 days.[3][8]

The space velocity components of this star system are U = +14.257, V = +0.915 and W = +3.147 km/s. α CrB is believed to be a member of the Ursa Major Moving Group of stars that have a common motion through space.[15]

Nomenclature

File:CoronaBorealisCC.jpg
α CrB, the brightest star in Corona Borealis

α Coronae Borealis (Latinised to Alpha Coronae Borealis) is the star's Bayer designation.

It bore the traditional names Alphecca, Gemma, and Gnosia Stella Coronae. Alphecca is Arabic, short for نير الفكّة nayyir al-fakka "the bright (star) of the broken (ring of stars)". Gemma is Latin for "jewel". Also Latin in origin is Gnosia Stella Coronae "Cretan star of the Crown" (specifically from Vergil's Georgics),[16] from Gnōsus or Gnōsos ("Knossos"), referencing the birthplace of Ariadne, whose wedding diadem became in some myths the constellation of Corona Borealis, following her marriage to Bacchus.[17] As the brightest star in Corona Borealis, it lent its name to Alphekka Meridiana, the brightest in the constellation of Corona Australis.Script error: No such module "Unsubst". The International Astronomical Union Working Group on Star Names (WGSN) has chosen Alphecca as the formal name for this star.[18]

The term nayyir al-fakka or Nir al Feccah appeared in the Al Achsasi Al Mouakket catalogue.[19]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Coiled Thong, refers to an asterism consisting of Alpha Coronae Borealis, Pi Coronae Borealis, Theta Coronae Borealis, Beta Coronae Borealis, Gamma Coronae Borealis, Delta Coronae Borealis, Epsilon Coronae Borealis, Iota Coronae Borealis and Rho Coronae Borealis.[20] Consequently, the Chinese name for Alpha Coronae Borealis itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.).[21]

In culture

Under the name Alphecca, this is one of the medieval Behenian fixed stars.

References

  1. ↑ a b c d e Script error: No such module "Citation/CS1". Vizier catalog entry
  2. ↑ Script error: No such module "Citation/CS1".
  3. ↑ a b c d Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ a b Script error: No such module "Citation/CS1".
  8. ↑ a b c d e Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Script error: No such module "Citation/CS1". Table 8.
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ Script error: No such module "Citation/CS1".
  15. ↑ Script error: No such module "Citation/CS1".
  16. ↑ Script error: No such module "citation/CS1".
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  21. ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.

Template:Stars of Corona Borealis

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