Tau8 Eridani

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.[5] The distance to this system can be estimated via the parallax method, yielding a value of around 380 light years.[2]

For other star systems with this Bayer designation, see Tau Eridani.
τ8 Eridani

A light curve for Tau8 Eridani, plotted from TESS data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 53m 42.70302s[2]
Declination −24° 36′ 44.0309″[2]
Apparent magnitude (V) 4.63 - 4.65[3]
Characteristics
Spectral type B6 V[4]
U−B color index −0.48[5]
B−V color index −0.13[5]
Variable type SPB[3]
Astrometry
Radial velocity (Rv)+23[6] km/s
Proper motion (μ) RA: +31.28[2] mas/yr
Dec.: −7.49[2] mas/yr
Parallax (π)8.65 ± 0.30 mas[2]
Distance380 ± 10 ly
(116 ± 4 pc)
Absolute magnitude (MV)−0.67[7]
Orbit[8]
Period (P)459±4 d
Eccentricity (e)0.18±0.02
Periastron epoch (T)2450954±7 JD
Argument of periastron (ω)
(secondary)		106±5°
Semi-amplitude (K1)
(primary)		21.7±0.4 km/s
Details
τ8 Eri A
Mass5.0±0.1[9] M☉
Luminosity256[10] L☉
Surface gravity (log g)4.00[11] cgs
Temperature11,858[10] K
Rotational velocity (v sin i)30[4] km/s
Age32.8±9.9[9] Myr
Other designations
τ8 Eridani, τ8 Eri, 33 Eridani, CD−24°1945, HD 24587, HIP 18216, HR 1213, SAO 168925.[12]
Database references
SIMBADdata

This is a single-lined[13] spectroscopic binary star system with an orbital period of about 459 days and an eccentricity of 0.18.[8] The primary component is a B-type main sequence star with a stellar classification of B6 V.[4] It is a slowly pulsating B-type star that undergoes radial-velocity variation with a frequency of 1.1569 times per day.[13] The star has about five[9] times the mass of the Sun and shines with 256 times the Sun's luminosity.[10] The outer atmosphere has an effective temperature of 11,858[10] K and may possess a longitudinal magnetic field with a strength of −140±71 G.[14]

References
  1. MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 24 September 2022.
  2. 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, S2CID 18759600.
  3. "Tau 8 Eri", The International Variable Star Index, AAVSO – American Association of Variable Star Observers, retrieved 16 February 2018.
  4. 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.
  5. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  6. 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, vol. 30, p. 57, Bibcode:1967IAUS...30...57E.
  7. 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, S2CID 119257644.
  8. De Cat, P.; Aerts, C.; De Ridder, J.; Kolenberg, K.; Meeus, G.; Decin, L. (2000), "A study of bright southern slowly pulsating B stars. I. Determination of the orbital parameters and of the main frequency of the spectroscopic binaries", Astronomy and Astrophysics, 355: 1015, Bibcode:2000A&A...355.1015D.
  9. 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:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  10. 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, S2CID 118665352.
  11. 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:0910.2851, Bibcode:2010A&A...515A..74L, doi:10.1051/0004-6361/200911956, S2CID 54028925.
  12. "tau08 Eri", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2016-10-13.
  13. 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:1504.04490, Bibcode:2015MNRAS.450.1585S, doi:10.1093/mnras/stv715.
  14. 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:1112.3969, Bibcode:2012A&A...538A.129B, doi:10.1051/0004-6361/201118098, S2CID 119199060, A129.
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