Epsilon Capricorni

"Kastra" redirects here. For the DJ and musical artist, see Kastra (musical artist). For the Late Roman fortified camp, see Castra ad Fluvio Frigido.
Epsilon Capricorni
Location of ε Capricorni (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Capricornus
Right ascension 21h 37m 04.83068s[1]
Declination −19° 27′ 57.6464″[1]
Apparent magnitude (V) +4.62[2]
Characteristics
Spectral type B2.5 Vpe[3]
U−B color index −0.64[2]
B−V color index −0.19[2]
Variable type γ Cas[4]
Astrometry
Proper motion (μ) RA: +12.79[1] mas/yr
Dec.: +0.28[1] mas/yr
Parallax (π)3.09 ± 0.18 mas[1]
Distance1,060 ± 60 ly
(320 ± 20 pc)
Absolute magnitude (MV)−3.03[5]
Details
ε Cap A
Mass7.6[6] M☉
Radius4.80[6] R☉
Luminosity4,649[5] L☉
Surface gravity (log g)4.0[6] cgs
Temperature18,800[6] K
Metallicity [Fe/H]−0.08[5] dex
Rotational velocity (v sin i)225[7] km/s
Age27.5±4.2[8] Myr
Other designations
Kastra,[9] ε Cap, 39 Cap, BD−20°6251, FK5 3724, HD 205637, HIP 106723, HR 8260, SAO 164520, WDS J21371-1928A[10]
Database references
SIMBADdata

Epsilon Capricorni, Latinized from ε Capricorni, is a possible binary star system[11][12] in the constellation Capricornus. It has the traditional star name Kastra, meaning "fort" or "military camp" in Latin. Based upon an annual parallax shift of 3.09 mas as seen from the Earth,[1] the star is located about 1,060 light years from the Sun. It can be seen with the naked eye, having a combined apparent visual magnitude of 4.62.[2]

In Chinese, 壘壁陣 (Lěi Bì Zhèn), meaning Line of Ramparts, refers to an asterism consisting of ε Capricorni, κ Capricorni, γ Capricorni, δ Capricorni, ι Aquarii, σ Aquarii, λ Aquarii, φ Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium.[13] Consequently, the Chinese name for ε Capricorni itself is 壘壁陣二 (Lěi Bì Zhèn èr, English: the Second Star of Line of Ramparts.)[14]

A light curve for Epsilon Capricorni, adapted from Lefèvre et al. (2009)[15]

The binary system has an orbital period of 129 days. The primary, component Aa, is a Be star that is surrounded by ionized gas that is producing the emission lines in the spectrum. This circumstellar shell is inclined by 80° to the line of sight from the Earth.[6] The system is undergoing both short term and long term variations in luminosity, with the short period variations showing a phase cycle of 1.03 days.[4] It is classified as a Gamma Cassiopeiae variable with an amplitude of 0.16 in magnitude.[4]

Epsilon Capricorni Aa is a blue-white hued B-type main sequence star with a stellar classification of B2.5 Vpe[3] and a visual magnitude of +4.62.[2] It has 7.6 times the mass of the Sun and 4.8 times the Sun's radius.[6] The star is spinning rapidly, with a projected rotational velocity of 225 km/s. This is giving it an oblate shape with an equatorial bulge that is 7% larger than the polar radius.[7]

The system has two visual companions. Component B is a visual magnitude 10.11 star at an angular separation of 65.8 arc seconds along a position angle of 46°, as of 2013. Component C with visual magnitude of 14.1 lies at an angular separation of 62.7 arc seconds along a position angle of 164°, as of 1999.[12] Both stars are likely to be unrelated and at different distances to Epsilon Capricorni.[16]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Feinstein1979 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Adelman2000 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Balona2002 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d e f Cite error: The named reference Silaj2014 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference belle2012 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Tetzlaff2011 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference kostjuk was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference zh was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference AEEA was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Lefèvre was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference dr3 was invoked but never defined (see the help page).