24 Ursae Majoris

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This article is about d Ursae Majoris. It is not to be confused with δ Ursae Majoris.
24 Ursae Majoris

A light curve for DK Ursae Majoris, plotted from Hipparcos data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 09h 34m 28.86175s[2]
Declination +69° 49′ 49.2265″[2]
Apparent magnitude (V) 4.54[3]
Characteristics
Spectral type G4 III-IV[4]
B−V color index 0.781±0.011[3]
Variable type RS CVn[5]
Astrometry
Radial velocity (Rv)−27.0±0.2[3] km/s
Proper motion (μ) RA: −64.785[2] mas/yr
Dec.: +77.214[2] mas/yr
Parallax (π)30.9269 ± 0.1621 mas[2]
Distance105.5 ± 0.6 ly
(32.3 ± 0.2 pc)
Absolute magnitude (MV)2.16±0.013[6]
Details
Mass1.9[7] M☉
Radius4.6[7] R☉
Luminosity14.9[7] L☉
Surface gravity (log g)3.44[6] cgs
Temperature5,335[6] K
Metallicity [Fe/H]−0.19[6] dex
Rotation10 d[7]
Rotational velocity (v sin i)5.5[8] km/s
Age1.0±0.1[9] Gyr
Other designations
d UMa, 24 UMa, DK UMa, BD+70°565, FK5 357, HD 82210, HIP 46977, HR 3771, SAO 6897[10]
Database references
SIMBADdata

24 Ursae Majoris is a variable star in the northern circumpolar constellation of Ursa Major, located 101.5 light-years from the Sun.[2] It has the variable star designation DK Ursae Majoris and the Bayer designation d Ursae Majoris; 24 Ursae Majoris is the Flamsteed designation. This object is visible to the naked eye as a faint, yellow-hued star with an apparent visual magnitude of 4.54.[3] It is moving closer to the Earth with a heliocentric radial velocity of −27 km/s, and is expected to come as close as 51 light-years in around 879,000 years.[failed verification][3]

Description[edit]

24 Ursae Majoris has a stellar classification of G4 III-IV,[4] which, at the estimated age of about one billion years,[9] matches the spectrum of an aging giant star blended with features of a subgiant luminosity class. Based upon its position on the H–R diagram, this star has just passed through the Hertzsprung gap and is ready to begin its first ascent along the red-giant branch.[11] It is a suspected RS Canum Venaticorum variable that changes in brightness by up to 0.058 in magnitude.[5] Periods of 22.08[12] and 2.115[13] hours have been reported. It is an X-ray source with a luminosity of 207.4×1028 erg s−1.[14]

This star has 1.9[7] times the mass of the Sun and has expanded to 4.6 times the Sun's radius. It is spinning with a rotation period of 10 days.[7] The star is radiating 14.9[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,335 K.[6]

Nomenclature[edit]

With π1, π2, σ1, σ2, ρ and 2 Ursae Majoris, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle.[15] 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 : 2 Ursae Majoris as Althiba I, π1 as Althiba II, π2 as Althiba III, ρ as Althiba IV, σ1 as Althiba V, σ2 as Althiba VI, and this star (d) as Althiba VII.[16]

References[edit]

  1. ^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
  2. ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. ^ a b c d e 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, S2CID 119257644.
  4. ^ a b Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  5. ^ a b Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. ^ a b c d e Park, Sunkyung; et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal, 146 (4): 73, arXiv:1307.0592, Bibcode:2013AJ....146...73P, doi:10.1088/0004-6256/146/4/73, S2CID 119187733.
  7. ^ a b c d e f g Gondoin, P. (December 2005), "The relation between X-ray activity and rotation in intermediate-mass G giants", Astronomy and Astrophysics, 444 (2): 531–538, Bibcode:2005A&A...444..531G, doi:10.1051/0004-6361:20053567.
  8. ^ Ayres, Thomas R.; et al. (July 2007), "X-Ray and Ultraviolet Spectroscopy of Intermediate-Mass, First Crossing Giants", The Astrophysical Journal Supplement Series, 171 (1): 304–330, Bibcode:2007ApJS..171..304A, doi:10.1086/516713
  9. ^ a b Pace, G. (March 2013), "Chromospheric activity as age indicator. An L-shaped chromospheric-activity versus age diagram", Astronomy & Astrophysics, 551: 4, arXiv:1301.5651, Bibcode:2013A&A...551L...8P, doi:10.1051/0004-6361/201220364, S2CID 56420519, L8.
  10. ^ "24 UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-17.
  11. ^ Simon, Theodore (January 1999), "DK UMa: A Star on the Ascent", Technical Report, vol. 01, Honolulu, HI United States: Hawaii University Institute for Astronomy, p. 16106, Bibcode:1999STIN...0116106S.
  12. ^ "DK UMa". The International Variable Star Index. AAVSO. Retrieved 1 December 2022.
  13. ^ Koen, Chris; Eyer, Laurent (March 2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331 (1): 45–59. arXiv:astro-ph/0112194. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x.
  14. ^ Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000), "Evolution of X-ray activity of 1–3 Msun late-type stars in early post-main-sequence phases", Astronomy and Astrophysics, 361: 614–628, Bibcode:2000A&A...361..614P
  15. ^ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 444
  16. ^ 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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