Omega² Scorpii

ω² Scorpii, Latinised as Omega² Scorpii, is a suspected[10] variable star in the zodiac constellation of Scorpius. A component of the visual double star ω Scorpii, it is bright enough to be seen with the naked eye having an apparent visual magnitude of +4.320.[2] The distance to this star, as determined using parallax measurements,[1] is around 291 light years. The visual magnitude of this star is reduced by 0.38 because of extinction from interstellar dust.[5]

For other stars with this Bayer designation, see ω Scorpii

ω² Scorpii

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Scorpius
Right ascension	16^h 07^m 24.32818^s[1]
Declination	−20° 52′ 07.5518″[1]
Apparent magnitude (V)	+4.320[2]
Characteristics
Spectral type	G6/8III[3]
U−B color index	+0.494[2]
B−V color index	+0.850[2]
Astrometry
Radial velocity (Rv)	−5.4[4] km/s
Proper motion (μ)	RA: +44.81[1] mas/yr Dec.: −45.42[1] mas/yr
Parallax (π)	11.22 ± 0.32[1] mas
Distance	291 ± 8 ly (89 ± 3 pc)
Absolute magnitude (MV)	−0.62[5]
Details
Mass	3.27[5] M☉
Radius	15.6[6] R☉
Luminosity	141[7] L☉
Surface gravity (log g)	2.62±0.11[8] cgs
Temperature	5,363±42[8] K
Metallicity [Fe/H]	+0.03±0.05[8] dex
Age	282[5] Myr
Other designations
Jabhat al Akrab, ω^2 Sco, 10 Scorpii, BD−20° 4408, HD 144608, HIP 78990, HR 5997, SAO 184135.[9]
Database references
SIMBAD	data

It is 0.05 degree north of the ecliptic, so can be occulted by the moon and planets.

This is a G-type giant star with a stellar classification of G6/8III.[3] With an estimated age of 282 million years,[5] it is an evolved, thin disk star that is currently on the red horizontal branch.[11] The interferometry-measured angular diameter of this star is 1.63 ± 0.10 mas,[12] which, at its estimated distance, equates to a physical radius of nearly 16 times the radius of the Sun.[6] It has 3.27 times the mass of the Sun,[5] and radiates 141 times the Sun's luminosity[7] The effective temperature of the star's outer atmosphere is 5,363 K.[8]

Names

In the Cook Islands, a traditional story is told of twins who flee their parents into the sky and become the pair of stars Omega² and Omega¹ Scorpii. The girl, who is called Piri-ere-ua "Inseparable", keeps tight hold of her brother, who is not named.[13] (The IAU used a version of this story from Tahiti to name Mu² Scorpii.)

References

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.
2. Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series, 61: 387–405, Bibcode:1985A&AS...61..387K.
3. Houk, N.; Smith-Moore, M. (1988), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Declinations -26°.0 to -12°.0, 4, Bibcode:1988mcts.book.....H.
4. Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W.
5. Takeda, Yoichi; et al. (August 2008), "Stellar Parameters and Elemental Abundances of Late-G Giants", Publications of the Astronomical Society of Japan, 60 (4): 781–802, arXiv:0805.2434, Bibcode:2008PASJ...60..781T, doi:10.1093/pasj/60.4.781.
6. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(89\cdot 1.63\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 31.2\cdot R_{\bigodot }\end{aligned}}}$

7. McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x.
8. Prugniel, P.; et al. (2011), "The atmospheric parameters and spectral interpolator for the MILES stars", Astronomy & Astrophysics, 531: A165, arXiv:1104.4952, Bibcode:2011A&A...531A.165P, doi:10.1051/0004-6361/201116769.
9. "* ome02 Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-25.
10. Sterken, C. (January 1977), "uvby Photometry of the Suspected Variable omega2 Sco", Information Bulletin on Variable Stars, 1230: 1, Bibcode:1977IBVS.1230....1S.
11. Afşar, M.; et al. (July 2012), "Chemical Compositions of Thin-disk, High-metallicity Red Horizontal-branch Field Stars", The Astronomical Journal, 144 (1): 20, arXiv:1205.3659, Bibcode:2012AJ....144...20A, doi:10.1088/0004-6256/144/1/20, 20.
12. Richichi, A.; Percheron, I. (May 2002), "CHARM: A Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 386: 492–503, Bibcode:2002A&A...386..492R, CiteSeerX 10.1.1.170.2863, doi:10.1051/0004-6361:20020236.
13. Johannes Carl Andersen (1931) Myths and Legends of the Polynesians. 1995 Dover reprint, p.399–400.

External links

• Kaler, James B. (September 9, 2016), "Omega-1 and Omega-2 Scorpii", Stars, University of Illinois, retrieved 2016-09-26.