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]
| 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[1] mas |
| Distance | approx. 900 ly (approx. 270 pc) |
| Absolute magnitude (MV) | −4.0[2] |
| Details | |
| Mass | 7.9±0.1[3] M☉ |
| Radius | 15[5] R☉ |
| Luminosity | 3,162[2] L☉ |
| Surface gravity (log g) | 2.42[2] cgs |
| Temperature | 8,128[2] K |
| Rotational velocity (v sin i) | 23[6] km/s |
| Age | 39.8±4.9[3] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
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]
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[9] 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
- 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.
- 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.
- 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.
- 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.
- 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: 521–24, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451.
- 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.
- "omi Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-09-22.
- Whittet, D. C. B. (February 1988), "On the nature and environment of Omicron Scorpii", Monthly Notices of the Royal Astronomical Society, 230: 473–478, Bibcode:1988MNRAS.230..473W, doi:10.1093/mnras/230.3.473.
- 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.