Tau8 Eridani

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τ8 Eridani
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 53m 42.70302s[1]
Declination −24° 36′ 44.0309″[1]
Apparent magnitude (V) 4.65[2]
Spectral type B6 V[3]
U−B color index −0.48[2]
B−V color index −0.13[2]
Radial velocity (Rv) +23[4] km/s
Proper motion (μ) RA: +31.28[1] mas/yr
Dec.: −7.49[1] mas/yr
Parallax (π) 8.65 ± 0.30[1] mas
Distance 380 ± 10 ly
(116 ± 4 pc)
Absolute magnitude (MV) −0.67[5]
Period (P) 459±4 d
Eccentricity (e) 0.18±0.02
Periastron epoch (T) 2450954±7 JD
Argument of periastron (ω)
Semi-amplitude (K1)
21.7±0.4 km/s
τ8 Eri A
Mass 5.0±0.1[7] M
Luminosity 256[8] L
Surface gravity (log g) 4.00[9] cgs
Temperature 11,858[8] K
Rotational velocity (v sin i) 30[3] km/s
Age 32.8±9.9[7] Myr
Other designations
τ8 Eridani, τ8 Eri, 33 Eridani, CD−24° 1945, HD 24587, HIP 18216, HR 1213, SAO 168925.[10]
Database references

Tau8 Eridani, Latinized from τ8 Eridani, is a binary star system in the constellation Eridanus. It is visible to the naked eye with a combined apparent visual magnitude of 4.65.[2] The distance to this system can be estimated via the parallax method, yielding a value of around 380 light years.[1]

This is a single-lined[11] spectroscopic binary star system with an orbital period of about 459 days and an eccentricity of 0.18.[6] The primary component is a B-type main sequence star with a stellar classification of B6 V.[3] It is a slowly pulsating B-type star that undergoes radial-velocity variation with a frequency of 1.1569 times per day.[11] The star has about five[7] times the mass of the Sun and shines with 256 times the Sun's luminosity.[8] The outer atmosphere has an effective temperature of 11,858[8] K and may possess a longitudinal magnetic field with a strength of −140±71 G.[12]


  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 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. ^ a b c Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590. 
  4. ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E. 
  5. ^ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971Freely accessible, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015. 
  6. ^ a b Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573Freely accessible, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213. 
  7. ^ a b c Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883Freely accessible, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x. 
  8. ^ a b c d 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. 
  9. ^ Lefever, K.; et al. (June 2010), "Spectroscopic determination of the fundamental parameters of 66 B-type stars in the field-of-view of the CoRoT satellite", Astronomy and Astrophysics, 515: A74, arXiv:0910.2851Freely accessible, Bibcode:2010A&A...515A..74L, doi:10.1051/0004-6361/200911956. 
  10. ^ "tau08 Eri -- Spectroscopic binary", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13. 
  11. ^ a b Szewczuk, W.; Daszyńska-Daszkiewicz, J. (June 2015), "Identification of pulsational modes in rotating slowly pulsating B-type stars", Monthly Notices of the Royal Astronomical Society, 450 (2): 1585–1603, arXiv:1504.04490Freely accessible, Bibcode:2015MNRAS.450.1585S, doi:10.1093/mnras/stv715. 
  12. ^ Bagnulo, S.; Landstreet, J. D.; Fossati, L.; Kochukhov, O. (February 2012), "Magnetic field measurements and their uncertainties: the FORS1 legacy", Astronomy & Astrophysics, 538: 22, arXiv:1112.3969Freely accessible, Bibcode:2012A&A...538A.129B, doi:10.1051/0004-6361/201118098, A129.