Sigma1_Ursae_Majoris

Sigma<sup>1</sup> Ursae Majoris

Sigma1 Ursae Majoris

Solitary star in the constellation Ursa Major

Sigma1 Ursae Majoris (σ1 UMa) is the Bayer designation for a solitary[8] star in the northern circumpolar constellation of Ursa Major. With an apparent visual magnitude of 5.14[2] it is faintly visible to the naked eye on dark nights. Based upon an annual parallax shift of 6.26 mas,[1] it is located roughly 520 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.06[3] due to interstellar dust.

For other stars with this Bayer designation, see σ Ursae Majoris.
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This is an evolved K-type giant star with a stellar classification of K5 III.[3] It is a suspected variable with an amplitude of 0.03 magnitude.[3] The measured angular diameter of the star after correcting for limb darkening is 2.67±0.04 mas,[9] which, at the estimated distance of this star, yields a physical size of about 46 times the radius of the Sun.[5] The star is radiating around 560[3] times the solar luminosity from its outer atmosphere at an effective temperature of 3,940 K.[6]

Naming

With π1, π2, σ2, ρ, A and d, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle.[10] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Ṭhibā were the title for seven stars : A as Althiba I, this star (π1) as Althiba II, π2 as Althiba III, ρ as Althiba IV, this star (σ1) as Althiba V, σ2 as Althiba VI, and d as Althiba VII.[11]

References

  1. [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, S2CID 18759600.
  2. [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    Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.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. [3]
    Groenewegen, M. A. T. (April 2012), "Infrared excess around nearby red giant branch stars and Reimers law", Astronomy & Astrophysics, 540: 21, Bibcode:2012A&A...540A..32G, doi:10.1051/0004-6361/201118287, A32.
  4. [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, S2CID 59451347, A61.
  5. [5]
    Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  6. [6]
    Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
  7. [7]
    "sig01 UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-25.{{cite web}}: CS1 maint: postscript (link)
  8. [8]
    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, S2CID 14878976.
  9. [9]
    Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
  10. [10]
    Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 444
  11. [11]
    Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology.
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