1 Scorpii

1 Scorpii, or b Scorpii, is a single[9] star in the southern zodiac constellation of Scorpius. It has an apparent magnitude of 4.63,[2] which is bright enough to be faintly visible to the naked eye on a dark night. The star shows an annual parallax shift of 6.59 mas from Earth's orbit, which equates to a distance of roughly 490 light years. It is a probable (89% chance) member of the Sco OB2 moving group.[10][9]

This article is about b Scorpii. It is not to be confused with β Scorpii.
1 Scorpii
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Scorpius
Right ascension 15h 50m 58.74452s[1]
Declination −25° 45′ 04.6649″[1]
Apparent magnitude (V) 4.63[2]
Characteristics
Spectral type B1.5 Vn[3]
B−V color index −0.072±0.003[2]
Astrometry
Radial velocity (Rv)−3.0±4.7[4] km/s
Proper motion (μ) RA: −14.20[1] mas/yr
Dec.: −25.12[1] mas/yr
Parallax (π)6.59 ± 0.27 mas[1]
Distance490 ± 20 ly
(152 ± 6 pc)
Absolute magnitude (MV)−1.27[2]
Details
Mass8.3±0.2[5] M☉
Radius3.7[6] R☉
Luminosity3,890[6] L☉
Temperature24,000[6] K
Rotational velocity (v sin i)310[7] km/s
Age10.3±5.3[5] Myr
Other designations
b Sco, 1 Sco, CD−25° 11131, HD 141637, HIP 77635, HR 5885, SAO 183854[8]
Database references
SIMBADdata

This is a B-type main-sequence star with a stellar classification of B1.5 Vn,[3] where the 'n' suffix indicates "nebulous" absorption lines being induced by rapid rotation. It has a projected rotational velocity of 310 km/s, which is giving the star an oblate shape with an equatorial bulge that is 13% wider than the polar radius.[7] There is some weak evidence that this is a Be star with a gaseous disk that is being viewed edge-on.[11]

1 Scorpii is a young star at around 10[5] million years old, with 8.3[5] times the mass of the Sun and 3.7 times the Sun's radius.[6] The star is radiating 3,890 times the Sun's luminosity from its photosphere at an effective temperature of about 24,000 K.[6]

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, S2CID 18759600.
  2. 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. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  5. 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.
  6. Hernández, J. S.; et al. (2005), "Herbig Ae/Be Stars in nearby OB Associations", The Astronomical Journal, 129 (2): 856, arXiv:astro-ph/0410494, Bibcode:2005AJ....129..856H, doi:10.1086/426918, S2CID 17672346.
  7. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
  8. "b Sco". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-21.
  9. 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.
  10. Rizzuto, Aaron; et al. (October 2011), "Multidimensional Bayesian membership analysis of the Sco OB2 moving group", Monthly Notices of the Royal Astronomical Society, 416 (4): 3108–3117, arXiv:1106.2857, Bibcode:2011MNRAS.416.3108R, doi:10.1111/j.1365-2966.2011.19256.x, S2CID 54510608.
  11. Rivinius, Th.; et al. (November 2006), "Bright Be-shell stars", Astronomy and Astrophysics, 459 (1): 137−145, Bibcode:2006A&A...459..137R, doi:10.1051/0004-6361:20053008.
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