Tau1 Arietis

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τ1 Arietis
Aries constellation map.svg
Red circle.svg
Location of τ1 Arietis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aries
Right ascension  03h 21m 13.62411s[1]
Declination +21° 08′ 49.5150″[1]
Apparent magnitude (V) 5.27[2]
Spectral type B5 IV[3]
U−B color index –0.53[2]
B−V color index –0.06[2]
Radial velocity (Rv)+14[4] km/s
Proper motion (μ) RA: +20.98[1] mas/yr
Dec.: –21.80[1] mas/yr
Parallax (π)6.41 ± 0.73[1] mas
Distanceapprox. 510 ly
(approx. 160 pc)
Absolute magnitude (MV)−0.66[5]
Mass5.0 ± 0.1[6] M
Radius3.4–3.6[7] R
Luminosity234[5] L
Rotational velocity (v sin i)30[8] km/s
Age54.8 ± 5.4[6] Myr
Other designations
τ1 Ari, 61 Arietis, BD+20 543, FK5 1094, HD 20756, HIP 15627, HR 1005, SAO 75886.[9]
Database references

Tau1 Arietis, Latinized from τ1 Arietis, is the Bayer designation for a triple star system[10] in the northern constellation of Aries. Based upon an annual parallax shift of 6.41 mas,[1] it is approximately 510 light-years (160 parsecs) distant from Earth. The combined apparent visual magnitude is 5.27,[2] making it faintly visible to the naked eye.

The inner pair form an eclipsing binary system, with the brightness of the pair decreasing by 0.06 in magnitude during an eclipse of the primary.[11] The third component is located at an angular separation of 0.810 arcseconds and has a magnitude of 8.17.[10] The primary component is a subgiant star with a stellar classification of B5 IV,[3] it has around 3.5[7] times the size of the Sun with five[6] times the Sun's radius.

This system is a member of the Cas-Tau OB association of stars that share a common motion through space.[12]


  1. ^ a b c d e f van Leeuwen, F. (November 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. ^ a b c d Crawford, D. L.; Barnes, J. V.; Golson, J. C. (1971), "Four-color, H-beta, and UBV photometry for bright B-type stars in the northern hemisphere", The Astronomical Journal, 76: 1058, Bibcode:1971AJ.....76.1058C, doi:10.1086/111220.
  3. ^ a b Lesh, Janet Rountree (December 1968), "The Kinematics of the Gould Belt: an Expanding Group?", Astrophysical Journal Supplement, 17: 371, Bibcode:1968ApJS...17..371L, doi:10.1086/190179.
  4. ^ Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  5. ^ a b 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. ^ a b c Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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.
  7. ^ a b Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
  8. ^ Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  9. ^ "tau01 Ari". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-11.
  10. ^ a b 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.
  11. ^ Malkov, O. Yu.; et al. (February 2006), "A catalogue of eclipsing variables", Astronomy and Astrophysics, 446 (2): 785–789, Bibcode:2006A&A...446..785M, doi:10.1051/0004-6361:20053137.
  12. ^ de Zeeuw, P. T.; et al. (January 1999), "A HIPPARCOS Census of the Nearby OB Associations", The Astronomical Journal, 117 (1): 354–399, arXiv:astro-ph/9809227, Bibcode:1999AJ....117..354D, doi:10.1086/300682.

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