2 Ursae Majoris
Location of 2 Ursae Majoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 08h 34m 36.17989s[1]
Declination +65° 08′ 42.4071″[1]
Apparent magnitude (V) 5.47[2]
Characteristics
Evolutionary stage main sequence[3]
Spectral type kA3hA5mA7s[4]
B−V color index +0.207[2]
Astrometry
Radial velocity (Rv)−16.87±0.13[1] km/s
Proper motion (μ) RA: −79.362[1] mas/yr
Dec.: −65.977[1] mas/yr
Parallax (π)21.7823 ± 0.1487 mas[1]
Distance150 ± 1 ly
(45.9 ± 0.3 pc)
Absolute magnitude (MV)2.12[2]
Details
Mass1.9[5] M☉
Radius1.8[5] R☉
Luminosity11.0[5] L☉
Surface gravity (log g)4.22[5] cgs
Temperature7,912[5] K
Metallicity [Fe/H]+0.19[6] dex
Rotational velocity (v sin i)11.9[6] km/s
Age560[7] Myr
Other designations
A UMa, 2 UMa, BD+65°638, HD 72037, HIP 42080, HR 3354[8]
Database references
SIMBADdata

2 Ursae Majoris (2 UMa) is an Am star in the northern circumpolar constellation of Ursa Major, located 150 light-years from the Sun. It has the Bayer designation A Ursae Majoris; 2 Ursae Majoris is the Flamsteed designation. It is visible to the naked eye as a faint white star with an apparent visual magnitude of 5.5. Currently 150 light years away, it is moving closer to the Earth with a heliocentric radial velocity of −17 km/s.[2]

Description

2 UMa has a stellar classification of kA3hA5mA7s, meaning it has hydrogen absorption lines typical of an A5 star, calcium K lines typical of an A3 star, and other metal absorption lines typical of an A7 star. This form of spectral type is used for Am stars, stars which show an over-abundance of metal lines in their spectrum due to slow rotation that allows stratification of elements within its photosphere. The 's' suffix indicates that the lines are sharp, another indicator of slow rotation. At an estimated age of 560 million years, 2 UMa is a main sequence star, fusing hydrogen into helium within its core. The projected rotational velocity is 11.9 km/s, very slow for a hot main sequence star.

This star has 1.9 times the mass of the Sun and 1.9 times its radius. It is radiating 11 times the Sun's luminosity from its photosphere at an effective temperature of 7,912 K.

Nomenclature

With π1, π2, σ1, σ2, ρ and 24 Ursae Majoris, it composed the Arabic asterism Al Ṭhibā᾽, the Gazelle.[9] 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 : this star as Althiba I, π1 as Althiba II, π2 as Althiba III, ρ as Althiba IV, σ1 as Althiba V, σ2 as Althiba VI, and 24 UMa as Althiba VII.[10]

References

  1. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 3 4 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.
  3. ↑ Burkhart, C. (1979). "The rotational velocity effect on the main sequence Am stars metallicity". Astronomy and Astrophysics. 74: 38. Bibcode:1979A&A....74...38B.
  4. ↑ Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  5. 1 2 3 4 5 Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
  6. 1 2 Takeda, Yoichi; Han, Inwoo; Kang, Dong-Il; Lee, Byeong-Cheol; Kim, Kang-Min (2019). "Compositional differences between the component stars of eclipsing close binary systems showing chemical peculiarities". Monthly Notices of the Royal Astronomical Society. 485 (1): 1067. arXiv:1902.04766. Bibcode:2019MNRAS.485.1067T. doi:10.1093/mnras/stz449.
  7. ↑ De Rosa, R. J.; et al. (January 2014). "The VAST Survey - III. The multiplicity of A-type stars within 75 pc". Monthly Notices of the Royal Astronomical Society. 437 (2): 1216–1240. arXiv:1311.7141. Bibcode:2014MNRAS.437.1216D. doi:10.1093/mnras/stt1932. S2CID 88503488.
  8. ↑ "2 UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-12-01.
  9. ↑ Allen, Richard Hinckley (1899), Star-Names and Their Meanings, New York: G. E. Stechert, p. 444
  10. ↑ 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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