Tau2 Lupi

Tau2 Lupi, Latinized from τ2 Lup, is a binary star[3] system in the constellation Lupus. It is visible to the naked eye with a combined apparent visual magnitude of 4.34.[2] Based upon an annual parallax shift of 10.22[1] mas as seen from Earth, it is located around 319 light years from the Sun. The two components orbit each other with a period of 26.2 years and a high eccentricity of 0.94.[6] The brighter component is a magnitude 4.93 subgiant star with a stellar classification of F4 IV. Its companion is an A-type star with visual magnitude 5.55 and class A7:.[3]

For other stars with this Bayer designation, see τ Lupi.
Tau2 Lupi
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Lupus
Right ascension 14h 26m 10.81378s[1]
Declination −45° 22′ 45.4023″[1]
Apparent magnitude (V) 4.34[2] (4.93 + 5.55)[3]
Characteristics
Spectral type F4 IV + A7:[3]
U−B color index +0.16[2]
B−V color index +0.43[2]
Astrometry
Radial velocity (Rv)−0.60±1.60[4] km/s
Proper motion (μ) RA: +14.62[1] mas/yr
Dec.: −7.33[1] mas/yr
Parallax (π)10.22 ± 0.31[1] mas
Distance319 ± 10 ly
(98 ± 3 pc)
Absolute magnitude (MV)−0.62[5]
Orbit[6]
Period (P)26.2 yr
Semi-major axis (a)0.125″
Eccentricity (e)0.94
Inclination (i)56.0°
Longitude of the node (Ω)175.7°
Periastron epoch (T)1969.1
Argument of periastron (ω)
(secondary)		191.0°
Details
Luminosity150[5] L☉
Rotational velocity (v sin i)0[7] km/s
Other designations
τ2 Lup, CD−44° 9323, HD 126354, HIP 70576, HR 5396, SAO 224920.[8]
Database references
SIMBADdata

References
  1. 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.
  2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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. 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.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. 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. Heintz, W. D. (August 1986), "Orbits of 20 visual binaries", Astronomy and Astrophysics Supplement Series, 65 (2): 411–417, Bibcode:1986A&AS...65..411H.
  7. Uesugi, Akira; Fukuda, Ichiro (1970), "Catalogue of rotational velocities of the stars", Contributions from the Institute of Astrophysics and Kwasan Observatory, University of Kyoto, Bibcode:1970crvs.book.....U.
  8. "tau02 Lup". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-03-10.
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