Epsilon Coronae Borealis

ε Coronae Borealis
Location of ε Coronae Borealis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Corona Borealis
Right ascension 15h 57m 35.25147s[1]
Declination +26° 52′ 40.3635″[1]
Apparent magnitude (V) 4.13[2]
Characteristics
Spectral type K2 III[2]
U−B color index +1.28[3]
B−V color index +1.235[3]
Astrometry
Radial velocity (Rv)–32.42[2] km/s
Proper motion (μ) RA: –77.07[1] mas/yr
Dec.: –60.61[1] mas/yr
Parallax (π)13.4922 ± 0.1023 mas[4]
Distance242 ± 2 ly
(74.1 ± 0.6 pc)
Absolute magnitude (MV)−0.02[5]
Details[6]
Mass1.37±0.24 M☉
Radius21.87+0.98
−0.99 R☉
Luminosity (bolometric)162.9±9.4 L☉
Surface gravity (log g)1.94±0.15[7] cgs
Temperature4,408±109 K
Metallicity [Fe/H]−0.22±0.03[7] dex
Rotational velocity (v sin i)2.4[8] km/s
Age3.24±1.81 Gyr
Other designations
13 Coronae Borealis, BD+27°2558, HD 143107, HIP 78159, HR 5947, SAO 84098, 2MASS J15573523+2652400[9]
Database references
SIMBADdata

Epsilon Coronae Borealis, Latinized from ε Coronae Borealis, is a multiple star system in the constellation Corona Borealis located around 230 light-years from the Solar System. It shines with a combined apparent magnitude of 4.13,[9] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations.[10] It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III,[11] which has exhausted its core fuel supply of hydrogen and swollen to 22 times the Sun's diameter and 163 times its luminosity.[6] That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit.[12] Its surface temperature has been calculated to be 4,365±9 K,[8] 4,408±109 K,[6] or 4,406±15 K.[11] It is thought to be around 3.2 billion years old.[6]

Epsilon Coronae Borealis B is a companion star thought to be an orange dwarf of spectral types K3V to K9V that orbits at a distance of 135 astronomical units, completing one orbit every 900 years.[12]

A faint (magnitude 11.5) star, 1.5 arc minutes away, has been called Epsilon Coronae Borealis C although it is only close by line of sight and is unrelated to the system.[12][13]

Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable T Coronae Borealis.[12]

  1. ^ a b c d Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference luck2015 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference EgUBV was invoked but never defined (see the help page).
  4. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Baines2018 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Mortier2013 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Archived from the original on 2014-03-31. Retrieved 2013-02-20.
  11. ^ a b Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D. E.; Kim, K.-M. (2012). "A planetary companion around the K giant ɛ Corona Borealis". Astronomy & Astrophysics. 546: 5. arXiv:1209.1187. Bibcode:2012A&A...546A...5L. doi:10.1051/0004-6361/201219347. S2CID 55260442. A5.
  12. ^ a b c d Kaler, James B. (19 August 2011). "Epsilon and T Coronae Borealis". Stars. University of Illinois. Retrieved 16 November 2014.
  13. ^ SIMBAD, CCDM J15576+2652C -- Star in double system (accessed 16 November 2014)