Omicron Scorpii

Omicron Scorpii (ο Sco, ο Scorpii) is a star in the zodiac constellation of Scorpius. With an apparent visual magnitude of +4.57,[2] it is visible to the naked eye. Parallax measurements indicate a distance of roughly 900 light years. It is located in the proximity of the Rho Ophiuchi dark cloud.[8]

ο Scorpii
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 16h 20m 38.18068s[1]
Declination −24° 10′ 09.5491″[1]
Apparent magnitude (V) +4.57[2]
Characteristics
Spectral type A4II/III[3]
B−V color index 0.5125[2]
Astrometry
Radial velocity (Rv)−8.2[4] km/s
Proper motion (μ) RA: −4.32[1] mas/yr
Dec.: −14.15[1] mas/yr
Parallax (π)3.71 ± 0.54 mas[1]
Distanceapprox. 900 ly
(approx. 270 pc)
Absolute magnitude (MV)−4.0[2]
Details
Mass7.9±0.1[3] M☉
Radius15[5] R☉
Luminosity3,162[2] L☉
Surface gravity (log g)2.42[2] cgs
Temperature8,128[2] K
Rotational velocity (v sin i)23[6] km/s
Age39.8±4.9[3] Myr
Other designations
ο Sco, 19 Scorpii, CD−23° 12849, HD 147084, HIP 80079, HR 6081, SAO 184329.[7]
Database references
SIMBADdata

This is a white A-type bright giant with a stellar classification of A4II/III.[3] It is one of the brighter members of this rare class of stars, making it of interest for study.[8] Omicron Scorpii has about eight times the mass of the Sun, fifteen times the radius,[5] and is roughly 40 million years old.[3] The star is radiating around 3,200 times the luminosity of the Sun from its outer atmosphere at an effective temperature of about 8,128 K.[2] It does not display an infrared excess due to circumstellar dust or a possible infrared-bright companion, but the light from this star is subject to extinction from interstellar dust.[8]

This star was originally designated by Lacaille as o Scorpii (lowercase Latin o) instead of omicron, but this designation was reinterpreted as Omicron Scorpii when the star originally designated by Bayer as Omicron Scorpii was reassigned to Libra as Upsilon Librae.[9]: 196, 278 

Omicron Scorpii was occasionally mentioned as a possible member of the Upper Scorpius sub-group in the Scorpius–Centaurus OB association during the 20th century.[2] However, it does not appear in more recent membership lists for this group[10] due to its small proper motion and small trigonometric parallax as measured by Hipparcos. This suggests that it is a background star unrelated to Scorpius–Centaurus.

References
  1. van Leeuwen, F. (November 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, S2CID 18759600.
  2. de Geus, E. J.; et al. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D.
  3. Tetzlaff, N.; et al. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
  4. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  5. Pasinetti Fracassini, L. E.; et al. (2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy & Astrophysics, 367 (2): 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
  6. Royer, F.; et al. (October 2012), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763.
  7. "omi Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-22.
  8. Whittet, D. C. B. (February 1988), "On the nature and environment of Omicron Scorpii", Monthly Notices of the Royal Astronomical Society, 230 (3): 473–478, Bibcode:1988MNRAS.230..473W, doi:10.1093/mnras/230.3.473.
  9. Wagman, Morton (2003). Lost Stars. McDonald & Woodward. ISBN 0939923785.
  10. de Zeeuw, P.T.; et al. (1999). "A Hipparcos Census of Nearby OB Associations". Astronomical Journal. 117 (1): 354–399. arXiv:astro-ph/9809227. Bibcode:1999AJ....117..354D. doi:10.1086/300682. S2CID 16098861.
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