Tau4 Eridani

For other star systems with this Bayer designation, see Tau Eridani.
τ4 Eri
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 19m 31.00224s[1]
Declination −21° 45′ 28.3049″[1]
Apparent magnitude (V) 3.65[2]
Characteristics
Spectral type M3/4 III[3]
U−B color index +1.79[2]
B−V color index +1.61[2]
Variable type Lb[4]
Astrometry
Radial velocity (Rv)+41.7±0.7[5] km/s
Proper motion (μ) RA: +51.89[1] mas/yr
Dec.: +32.92[1] mas/yr
Parallax (π)10.71 ± 0.54[1] mas
Distance300 ± 20 ly
(93 ± 5 pc)
Details
Mass1.8±0.3[6] M☉
Radius106[7] R☉
Luminosity1,537[8] L☉
Temperature3,712[6] K
Other designations
τ4 Eridani, τ4 Eri, 16 Eridani, BD-22° 584, HD 20720, HIP 15474, HR 1003, SAO 168460.[9]

Tau4 Eridani (τ4 Eri, τ4 Eri) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.65.[2] The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years.[1]

This is an evolved red giant star currently on the asymptotic giant branch[10] with a stellar classification of M3/4 III.[3] It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72[4] with a periodicity of 23.8 d.[11] The measured angular diameter of Tau4 Eridani is 10.58±1.00 mas.[12] At its estimated distance, this yields a physical size of about 106 times the radius of the Sun.[7] It shines with 1,537[8] times the luminosity of the Sun from an outer atmosphere at an effective temperature of 3,712 K.[6]

This is most likely a binary star system.[13] The companion is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013.[14]

References

  1. 1 2 3 4 5 6 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  2. 1 2 3 4 Mermilliod, J.-C. (1986), Compilation of Eggen's UBV data, transformed to UBV (unpublished), SIMBAD, Bibcode:1986EgUBV........0M.
  3. 1 2 Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, 4, Bibcode:1988MSS...C04....0H.
  4. 1 2 Ruban, E. V.; et al. (September 2006), "Spectrophotometric observations of variable stars", Astronomy Letters, 32 (9): 604–607, Bibcode:2006AstL...32..604R, doi:10.1134/S1063773706090052.
  5. ↑ Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
  6. 1 2 3 Halabi, Ghina M.; Eid, Mounib El (2015). "Exploring masses and CNO surface abundances of red giant stars". Monthly Notices of the Royal Astronomical Society. 451 (3): 2957. arXiv:1507.01517Freely accessible. Bibcode:2015MNRAS.451.2957H. doi:10.1093/mnras/stv1141.
  7. 1 2 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  8. 1 2 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. ↑ "tau04 Eri -- Long-period variable star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2016-10-13.
  10. ↑ Lebzelter, T.; Hron, J. (January 2008), "BRITE stars on the AGB", Communications in Asteroseismology, 152: 178–181, Bibcode:2008CoAst.152..178L, doi:10.1553/cia152s178.
  11. ↑ Tabur, V.; et al. (December 2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–1961, arXiv:0908.3228Freely accessible, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x.
  12. ↑ Richichi, A.; Percheron, I. (May 2005), "First results from the ESO VLTI calibrators program", Astronomy and Astrophysics, 434 (3): 1201–1209, arXiv:astro-ph/0501532Freely accessible, Bibcode:2005A&A...434.1201R, doi:10.1051/0004-6361:20042257.
  13. ↑ 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.
  14. ↑ Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
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