Gamma2 Normae

Gamma2 Normae, Latinized from γ2 Nor, is the brightest star in the southern constellation of Norma. Its apparent magnitude is 4.02[2] – making it a faint star but visible to the naked eye. Based upon an annual parallax shift of 25.33 mas as seen from Earth,[1] this star is located roughly 129 light years from the Sun. It is moving closer to the Sun with a radial velocity of −29 km/s.[4]

For other stars with this Bayer designation, see γ Normae.
Gamma2 Normae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Norma
Right ascension 16h 19m 50.42227s[1]
Declination −50° 09′ 19.8223″[1]
Apparent magnitude (V) 4.02[2]
Characteristics
Spectral type K0III[3]
U−B color index +1.16[2]
B−V color index +1.08[2]
Astrometry
Radial velocity (Rv)−28.9±0.7[4] km/s
Proper motion (μ) RA: −159.71[1] mas/yr
Dec.: −52.25[1] mas/yr
Parallax (π)25.33 ± 0.20[1] mas
Distance129 ± 1 ly
(39.5 ± 0.3 pc)
Absolute magnitude (MV)1.057[5]
Details
Mass2.16[5] M☉
Luminosity51[6] L☉
Surface gravity (log g)2.80[5] cgs
Temperature4,699[5] K
Metallicity [Fe/H]0.23[5] dex
Other designations
γ2 Nor, CD−49° 10536, GC 12216, GJ 9554, HD 146686, HIP 80000, HR 6072, SAO 243643[7]
Database references
SIMBADdata
ARICNSdata

This is an evolved, yellow-hued giant of spectral type K0 III[3] around 2.16[5] times as massive as the Sun that has swollen to a diameter 10 times that of the Sun.[8] It is a red clump star on the horizontal branch, which indicates it is generating energy through helium fusion at its core.[9] The star is radiating 51[6] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,699 K.[5]

Gamma2 Normae is a close double, with a magnitude 10 companion. The pair has been previously identified as a binary star system,[10] but the second release of Gaia data showed the companion star to be much more distant. Another 16-magnitude star, with a temperature of 5,972 K, is listed 20" away with nearly the same parallax and proper motion as Gamma2 Normae.[11]

γ1 Nor is a yellow supergiant located nearby on the celestial sphere, but is much further away from Earth and nearly a magnitude fainter.

References
  1. van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics. 474 (2): 653–64. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J.
  3. Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 2, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, S2CID 119231169.
  5. Liu, Y. J.; et al. (2007), "The abundances of nearby red clump giants", Monthly Notices of the Royal Astronomical Society, 382 (2): 553–66, Bibcode:2007MNRAS.382..553L, doi:10.1111/j.1365-2966.2007.11852.x.
  6. 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.
  7. "* gam02 Nor". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 22 December 2012.
  8. Kaler, James B. "Gamma-2 Normae". Stars. University of Illinois. Retrieved 23 March 2015.
  9. Laney, C. D.; et al. (January 2012), "A new Large Magellanic Cloud K-band distance from precision measurements of nearby red clump stars", Monthly Notices of the Royal Astronomical Society, 419 (2): 1637–1641, arXiv:1109.4800, Bibcode:2012MNRAS.419.1637L, doi:10.1111/j.1365-2966.2011.19826.x, S2CID 117788450.
  10. 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.
  11. 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.
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