Epsilon Capricorni

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Double star
ε Capricorni
ε Cap in the constellation "Capricorn"
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Capricorn
Right ascension 21 h 37 m 4.83 s
declination -19 ° 27 ′ 57.7 ″
Apparent brightness 4.45 likes
Typing
B − V color index −0.18 
U − B color index −0.66 
R − I index −0.14 
Spectral class B3 V
Variable star type γ Cas 
Astrometry
Radial velocity (−23.7 ± 0.9) km / s
parallax (3.09 ± 0.18)  mas
distance (1055 ± 65)  ly
(324 ± 20)  pc
Proper movement 
Rec. Share: (12.79 ± 0.17)  mas / a
Dec. portion: (0.28 ± 0.13)  mas / a
Physical Properties
Dimensions 8.8  M ☉
Luminosity

7230  L ☉

Effective temperature 18700  K
Metallicity [Fe / H] −0.08
Other names
and catalog entries
Bayer name ε Capricorni
Flamsteed name 39 Capricorni
Bonn survey BD −20 ° 6251
Bright Star Catalog HR 8260 [1]
Henry Draper Catalog HD 205637 [2]
Hipparcos catalog HIP 106723 [3]
SAO catalog SAO 164520 [4]
Tycho catalog TYC 6370-1176-1 [5]Template: Infobox star / maintenance / specification of the TYC catalog
2MASS catalog 2MASS 21370483-1927580 [6]
Other names WDS 21371-1928
CCDM 21371-1928

Epsilon Capricorni (ε Cap) is a visual multiple star in the constellation Capricorn . It has a total brightness of 4.4 mag and its distance is approximately 1055 light years .

The main star A is a blue-white main sequence star of about 9 times the mass and over 7000 times the luminosity of the sun , which is classified as a Be star because it shows special features in its spectrum, such as emission lines from the Balmer series . It is also an eruptive irregular variable of the Gamma Cassiopeiae type. These are rapidly rotating blue-white stars with matter flowing out of the equatorial zone. The formation of equatorial rings or discs is often associated with temporary drops in brightness. For Epsilon Capricorni A a very high projected equatorial rotation speed v ∙ sin i of about 230 km / s was measured.

In 1830, in addition to the bright blue-white star A , John Herschel found a companion B almost 180 times weaker with an apparent magnitude of 10.1 mag. This star also bears the designation BD −20 ° 6253. This is possibly an orange giant or sub-giant of the spectral class K1 III / IV: it is about 66 arc seconds away from the main star. In 1877 Sherburne Wesley Burnham was able to describe a third component C. This star has a brightness of only 14.1 mag and is now about 63 arc seconds away from the main star A.

The star Epsilon Capricorni is sometimes referred to with the proper name "Kastra" or "Castra" (from Latin castra , 'camp, barracks').

Individual evidence

  1. ↑ a b c d e VizieR: Hipparcos, the New Reduction (van Leeuwen, 2007) - The Astrometric Catalog
  2. ↑ a b VizieR: Stellar Photometry in Johnson's 11-color system (Ducati, 2002)
  3. ^ VizieR: Southern B and Be stars (Levenhagen +, 2006)
  4. ↑ VizieR: General Catalog of Stellar Radial Velocities (Wilson, 1953)
  5. ↑ VizieR: Young runaway stars within 3kpc (Tetzlaff +, 2011)
  6. ↑ a b c VizieR: Be star rotational velocities distribution (Zorec +, 2016)
  7. ↑ VizieR: Extended Hipparcos Compilation (XHIP) (Anderson +, 2012)
  8. ↑ VizieR: General Catalog of Variable Stars (Samus + 2007-2013)
  9. ↑ VizieR: Catalog of Stellar Spectral Classifications (Skiff, 2009-2016)
  10. ↑ VizieR: The Washington Visual Double Star Catalog (Mason + 2001-2014)