Astronomy:Tau Ursae Majoris

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Short description: Binary star in the constellation Ursa Major
Tau Ursae Majoris
Diagram showing star positions and boundaries of the Ursa Major constellation and its surroundings
12px
Location of τ Ursae Majoris (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Ursa Major
Right ascension  09h 10m 55.06553s[1]
Declination +63° 30′ 49.0553″[1]
Apparent magnitude (V) 4.66[2]
Characteristics
Spectral type kA5hF0mF5 II[3]
U−B color index +0.14[2]
B−V color index +0.35[2]
Astrometry
Radial velocity (Rv)−9.80±0.30[4] km/s
Proper motion (μ) RA: +102.37[1] mas/yr
Dec.: −63.55[1] mas/yr
Parallax (π)25.82 ± 0.54[1] mas
Distance126 ± 3 ly
(38.7 ± 0.8 pc)
Absolute magnitude (MV)+1.73[5]
Orbit[6]
Period (P)1,062.4 d
Eccentricity (e)0.48
Periastron epoch (T)2425721.6 JD
Argument of periastron (ω)
(secondary)		349.4°
Semi-amplitude (K1)
(primary)		3.9 km/s
Details
τ UMa A
Mass1.8±0.1[7] M☉
Luminosity16[8] L☉
Surface gravity (log g)3.86±0.43[9] cgs
Temperature7,343±100[9] K
Metallicity [Fe/H]+0.57±0.15[9] dex
Rotational velocity (v sin i)21[10] km/s
Other designations
τ UMa, 14 Ursae Majoris, BD+64°723, FK5 2727, HD 78362, HIP 45075, HR 3624, SAO 14796, WDS J09109+6331A[11]
Database references
SIMBADdata

Tau Ursae Majoris (τ UMa) is the Bayer designation for a binary star in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye, having an apparent visual magnitude of 4.66.[2] With an annual parallax shift of 25.82 mas,[1] it is located about 126 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.19 due to interstellar dust.[9]

This is a single-lined spectroscopic binary star system with an orbital period of 2.9 years and an eccentricity of 0.48.[6] The primary member, component A, is an evolved bright giant with a stellar classification of kA5hF0mF5 II.[3] This notation indicates the star's spectrum shows the calcium K lines of an A5 star, the hydrogen lines of an F0 star, and the metallic lines of an F5 star.[12] It is an evolved Am star of the ρ Puppis type, a class of evolved stars showing the Am chemical peculiarities.[13] It is located in the instability strip of the Hertzsprung–Russell diagram but is not thought to be variable.[7]

Naming

With φ, h, υ, θ, e, and f, it composed the Arabic asterism Sarīr Banāt al-Na'sh, the Throne of the daughters of Na'sh, and Al-Haud, the Pond.[14] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al-Haud were the title for seven stars : f as Alhaud I, this star (τ) as Alhaud II, e as Alhaud III, h as Alhaud IV, θ as Alhaud V, υ as Alhaud VI and φ as Alhaud VII .[15]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 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. ↑ 3.0 3.1 Gray, R. O. et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal 132 (1): 161–170, doi:10.1086/504637, Bibcode: 2006AJ....132..161G. 
  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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  5. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 Pourbaix, D.; Tokovinin, A. A.; Batten, A. H.; Fekel, F. C.; Hartkopf, W. I. et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy & Astrophysics 424 (2): 727–732, doi:10.1051/0004-6361:20041213, Bibcode: 2004A&A...424..727P. 
  7. ↑ 7.0 7.1 Burkhart, C. et al. (January 2005), "The field Am and ρ Puppis-like stars: Lithium and heavier elements", Astronomy and Astrophysics 429 (3): 1043–1049, doi:10.1051/0004-6361:20040467, Bibcode: 2005A&A...429.1043B. 
  8. ↑ McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M. 
  9. ↑ 9.0 9.1 9.2 9.3 Koleva, M.; Vazdekis, A. (February 2012), "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library", Astronomy & Astrophysics 538: A143, doi:10.1051/0004-6361/201118065, Bibcode: 2012A&A...538A.143K. 
  10. ↑ Royer, F. et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, doi:10.1051/0004-6361:20020943, Bibcode: 2002A&A...393..897R. 
  11. ↑ "tau UMa". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tau+UMa. 
  12. ↑ Gray, Richard O.; Corbally, J. (2009), Stellar Spectral Classification, Princeton University Press, pp. 178, ISBN 978-0691125114. 
  13. ↑ Zaremba, D. (1979), "On the determination of the stellar chemical composition. I - Tau UMa", Acta Astronomica 29 (4): 573–586, Bibcode: 1979AcA....29..573Z. 
  14. ↑ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 442. 
  15. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19720005197_1972005197.pdf. 



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