Epsilon Circini

Epsilon Circini, Latinized from ε Circini, is a solitary[9] star located in the southern constellation of Circinus. It is faintly visible to the naked eye, having an apparent visual magnitude of 4.86.[2] The distance to this star, as determined by a measured annual parallax shift of 8.00 mas,[1] is around 410 light years.

ε Circini
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Circinus
Right ascension  15h 17m 38.89127s[1]
Declination −63° 36′ 37.6789″[1]
Apparent magnitude (V) 4.86[2]
Characteristics
Spectral type K2.5 III[3]
U−B color index +1.32[2]
B−V color index +1.25[2]
Astrometry
Radial velocity (Rv)−4.6±0.8[4] km/s
Proper motion (μ) RA: +2.57[1] mas/yr
Dec.: +8.45[1] mas/yr
Parallax (π)8.00 ± 0.48[1] mas
Distance410 ± 20 ly
(125 ± 8 pc)
Absolute magnitude (MV)−0.63[5]
Details
Radius27[6] R☉
Luminosity243.6[7] L☉
Temperature4,576[7] K
Other designations
ε Cir, CPD−63° 3544, FK5 3205, HD 135291, HIP 74837, HR 5666, SAO 253088.[8]
Database references
SIMBADdata

This is an evolved K-type giant star with a stellar classification of K2.5 III.[3] The measured angular diameter of this star is 2.02±0.11 mas.[10] At its estimated distance, this yields a physical size of about 27 times the radius of the Sun.[6] It radiates about 244[7] times the solar luminosity from its outer atmosphere at an effective temperature of 4,576 K.[7]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. Landi Dessy, J.; Keenan, P. C. (November 1966), "Spectral Types on the MK System for Forty-Three Bright Southern Stars, K2-M6", Astrophysical Journal, 146: 587, Bibcode:1966ApJ...146..587L, doi:10.1086/148925.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
  8. "eps Cir -- Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2017-01-18.
  9. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  10. Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
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