Astronomy:24 Ursae Majoris
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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[2] mas |
| Distance | 105.5 ± 0.6 ly (32.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.16±0.013[6] |
| Details | |
| Mass | 1.9[7] M☉ |
| Radius | 4.6[7] R☉ |
| Luminosity | 14.9[7] L☉ |
| Surface gravity (log g) | 3.44[6] cgs |
| Temperature | 5,335[6] K |
| Metallicity [Fe/H] | −0.19[6] dex |
| Rotation | 10 d[7] |
| Rotational velocity (v sin i) | 5.5[8] km/s |
| Age | 1.0±0.1[9] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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
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
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
- ↑ "/ftp/cats/more/HIP/cdroms/cats". Strasbourg astronomical Data Center. https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 3.3 3.4 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 4.0 4.1 Keenan, Philip C.; McNeil, Raymond C. (1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series 71: 245, doi:10.1086/191373, Bibcode: 1989ApJS...71..245K.
- ↑ 5.0 5.1 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S.
- ↑ 6.0 6.1 6.2 6.3 6.4 Park, Sunkyung et al. (2013), "Wilson-Bappu Effect: Extended to Surface Gravity", The Astronomical Journal 146 (4): 73, doi:10.1088/0004-6256/146/4/73, Bibcode: 2013AJ....146...73P.
- ↑ 7.0 7.1 7.2 7.3 7.4 7.5 7.6 Gondoin, P. (December 2005), "The relation between X-ray activity and rotation in intermediate-mass G giants", Astronomy and Astrophysics 444 (2): 531–538, doi:10.1051/0004-6361:20053567, Bibcode: 2005A&A...444..531G.
- ↑ 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, doi:10.1086/516713, Bibcode: 2007ApJS..171..304A
- ↑ 9.0 9.1 Pace, G. (March 2013), "Chromospheric activity as age indicator. An L-shaped chromospheric-activity versus age diagram", Astronomy & Astrophysics 551: 4, doi:10.1051/0004-6361/201220364, L8, Bibcode: 2013A&A...551L...8P.
- ↑ "24 UMa". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=24+UMa.
- ↑ Simon, Theodore (January 1999), "DK UMa: A Star on the Ascent", Technical Report, 01, Honolulu, HI United States: Hawaii University Institute for Astronomy, p. 16106, Bibcode: 1999STIN...0116106S.
- ↑ "DK UMa". AAVSO. https://www.aavso.org/vsx/index.php?view=detail.top&oid=37237.
- ↑ 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. doi:10.1046/j.1365-8711.2002.05150.x. Bibcode: 2002MNRAS.331...45K.
- ↑ 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
- ↑ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 444
- ↑ 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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