Epsilon Coronae Borealis

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ε Coronae Borealis
Corona Borealis constellation map.svg
Red circle.svg

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) 14.73 ± 0.21[1] mas
Distance 221 ± 3 ly
(67.9 ± 1.0 pc)
Details
Mass 1.44±0.18[4] M
Radius 21[5] R
Luminosity (bolometric) 151[2] L
Surface gravity (log g) 1.94±0.15[4] cgs
Temperature 4,365±28[2] K
Metallicity [Fe/H] −0.22±0.03[4] dex
Rotational velocity (v sin i) 2.4[5] km/s
Age 4.13[2] Gyr
Other designations
12 Coronae Borealis, BD+27° 2558, HD 143107, HIP 78159, HR 5947, SAO 84098[6]
Database references
SIMBAD data

Epsilon Coronae Borealis (ε CrB) 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,[6] meaning it is visible to the unaided eye in all night skies except those brightly lit in inner city locations.[7] It is an orange giant around 1.7 times as massive as the Sun of spectral type K2III,[8] which has exhausted its core fuel supply of hydrogen and swollen to 21 times the Sun's diameter and 151 times its luminosity.[9] That is, Epsilon Coronae Borealis's diameter is about one-quarter of Mercury's orbit.[10] Its surface temperature has been calculated to be 4365 ± 9 K,[9] or 4406 ± 15 K.[8] It is thought to be around 1.74 billion years old.[8]

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.[10]

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.[10][11]

The ε CrB star system's radial velocity was observed over seven years from January 2005 to January 2012, during which time a 'wobble' with a period of around 418 days was recorded. This has been calculated to be a planet around 6.7 times as massive as Jupiter orbiting at a distance of 1.3 astronomical units with an eccentricity of 0.11.[8]

Epsilon Coronae Borealis lies one degree north of (and is used as a guide for) the variable T Coronae Borealis.[10]

The Epsilon Coronae Borealis planetary system[12]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥6.7 ± 0.3 MJ 1.3 417.9 ± 0.5 0.11 ± 0.03

References[edit]

  1. ^ a b c d e van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752Freely accessible, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d e f Luck, R. Earle (2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 88, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88. 
  3. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Bibcode:1986EgUBV........0M. 
  4. ^ a b c Mortier, A.; et al. (September 2013), "New and updated stellar parameters for 71 evolved planet hosts. On the metallicity-giant planet connection", Astronomy & Astrophysics, 557: 19, arXiv:1307.7870Freely accessible, Bibcode:2013A&A...557A..70M, doi:10.1051/0004-6361/201321641, A70. 
  5. ^ a b Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209. 
  6. ^ a b "eps CrB -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-03-17. 
  7. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 2013-02-20. 
  8. ^ a b c d 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:1209.1187Freely accessible. Bibcode:2012A&A...546A...5L. doi:10.1051/0004-6361/201219347. A5. 
  9. ^ a b Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (January 2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal. 135 (1): 209–31. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209. 
  10. ^ a b c d Kaler, James B. (19 August 2011). "Epsilon and T Coronae Borealis". Stars. University of Illinois. Retrieved 16 November 2014. 
  11. ^ SIMBAD, CCDM J15576+2652C -- Star in double system (accessed 16 November 2014)
  12. ^ Jean Schneider (2003). "Planet eps CrB b". Extrasolar Planets Encyclopaedia. Retrieved 4 February 2017.