Chi Eridani

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χ Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 01h 55m 57.47212s[1]
Declination −51° 36′ 32.0325″[1]
Apparent magnitude (V) 3.70[2] / 10.7[3]
Spectral type G8IV[4]
U−B color index +0.46[2]
B−V color index +0.85[2]
Proper motion (μ) RA: +680.92[1] mas/yr
Dec.: −283.46[1] mas/yr
Parallax (π) 56.02 ± 0.38[1] mas
Distance 58.2 ± 0.4 ly
(17.9 ± 0.1 pc)
Absolute magnitude (MV) 2.39 / 9.4[3]
χ Eri A
Mass 1.58 M
Radius 4.06±0.16 R
Luminosity 392[6] L
Surface gravity (log g) 3.42±0.10 cgs
Temperature 5,135±80 K
Metallicity [Fe/H] −0.18±0.07 dex
Rotational velocity (v sin i) 2.0±1.0 km/s
Other designations
χ Eri, FK5 68, GJ 81, HD 11937, HIP 9007, HR 566, SAO 232573.[7]
Database references

χ Eridani (Latinised as Chi Eridani) is a binary star[8] system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.70.[2] The distance to this system, as determined using the parallax method, is around 58 light years.[1] The pair had an angular separation of 5.0 arcseconds as of 1994. This corresponds to a projected separation of around 128 AU.[3]

The primary component is an evolving G-type subgiant star with a stellar classification of G8 IV.[4] It is about 1.6 times the mass of the Sun and has 4 times the Sun's radius.[5] The star shines with 392[6] times the solar luminosity from its outer atmosphere at an effective temperature of 5,135 K.[5] Unusually for a star of this class, it shows a photometric variability of 0.04 in magnitude, which may be due to a previous mass transfer from the secondary companion, or else from an undiscovered third companion.[5]

The companion is about 7 magnitudes fainter than the primary and may be the source of the X -ray emission from this system. This emission has a luminosity of 504.4×1027 erg s−1.[5]


  1. ^ a b c d e f 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 ^ a b c d Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV data, SIMBAD, Bibcode:1986EgUBV........0M. 
  3. ^ a b c Poveda, A.; et al. (April 1994), "Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems", Revista Mexicana de Astronomía y Astrofísica, 28 (1): 43–89, Bibcode:1994RMxAA..28...43P.  See pp. 58–59.
  4. ^ a b Torres, C. A. O.; et al. (December 2006), "Search for associations containing young stars (SACY). I. Sample and searching method", Astronomy and Astrophysics, 460 (3): 695–708, arXiv:astro-ph/0609258Freely accessible, Bibcode:2006A&A...460..695T, doi:10.1051/0004-6361:20065602. 
  5. ^ a b c d e Fuhrmann, K.; Chini, R. (2012), "Multiplicity among F-type Stars", The Astrophysical Journal Supplement, 203 (2): 20, Bibcode:2012ApJS..203...30F, doi:10.1088/0067-0049/203/2/30, 30. 
  6. ^ a b 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:1208.2037Freely accessible, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x. 
  7. ^ "chi Eri -- Pre-main sequence Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-27. 
  8. ^ 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:0806.2878Freely accessible, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.