Omega Orionis

Omega Orionis (ω Ori) is a single[8] star in the constellation Orion. Its apparent magnitude is 4.57[2] and is located approximately 1,400 light-years from the Solar System. It is surrounded by a cloud of dust, forming a modest reflection nebula over a light-year wide.[9]

A visual band light curve for Omega Orionis, adapted from Balona et al. (2001)[10]
ω Orionis
Location of ω Orionis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Orion
Right ascension 05h 39m 11.14632s[1]
Declination +04° 07′ 17.2795″[1]
Apparent magnitude (V) 4.57[2]
Characteristics
Spectral type B3 Ve[3]
U−B color index −0.76[2]
B−V color index −0.11[2]
Astrometry
Radial velocity (Rv)20.4[4] km/s
Proper motion (μ) RA: +0.84[1] mas/yr
Dec.: +0.00[1] mas/yr
Parallax (π)2.36 ± 0.29 mas[1]
Distanceapprox. 1,400 ly
(approx. 420 pc)
Details
Mass7.0±0.5[3] M☉
Radius5.9[5] R☉
Luminosity6,031[6] L☉
Surface gravity (log g)3.59±0.10[3] cgs
Temperature19,000±500[3] K
Rotation1.37 d[5]
Rotational velocity (v sin i)179±4[5] km/s
Age43.6[3] Myr
Other designations
ω Ori, 47 Orionis, BD+04° 1002, FK5 2423, HD 37490, HIP 26594, HR 1934, SAO 113001.[7]
Database references
SIMBADdata

Omega Orionis is a B-type main sequence star of spectral type B3 Ve[3] with an effective temperature of 19,000 K.[3] Including a large amount of ultraviolet radiation, Omega Orionis shines with a Luminosity 6,031[6] times greater than the Sun's and it has a radius 5.9[5] times larger than solar radius, The projected rotation speed is 179 km/s – involves a period of 1.37[5] days rotation. However, actual rotation speed can reach 450 km/s, it estimated that its axis is inclined 24° relative to the line of sight.[9] The star has a mass 7.0[3] times that of the Sun, just below the limit beyond which stars explode as supernovas. Its age is estimated at 43.6[3] million years.

As a result of its rapid rotation, Omega Orionis is a Be class star. Among the stars of this class, Omega Orionis was the first where the magnetic field was measured and found to be 1000 times that of the Earth. Omega Orionis is, like many Be stars, a variable star whose brightness varies 0.19 magnitudes. Also, small variations have been observed due to non-radial pulsations with periods of 0.97 and 2.19 days.[9]

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. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Levenhagen, R. S.; Leister, N. V. (2006), "Spectroscopic Analysis of Southern B and Be Stars", Monthly Notices of the Royal Astronomical Society, 371 (1): 252–62, arXiv:astro-ph/0606149, Bibcode:2006MNRAS.371..252L, doi:10.1111/j.1365-2966.2006.10655.x, S2CID 16492030.
  4. Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, Veröffentlichungen des Astronomisches Rechen-Institut Heidelberg, 35: 1, Bibcode:1999VeARI..35....1W.
  5. Neiner, C.; et al. (November 2012), "An investigation of the magnetic properties of the classical Be star ω Ori by the MiMeS Collaboration", Monthly Notices of the Royal Astronomical Society, 426 (4): 2738–2750, Bibcode:2012MNRAS.426.2738N, doi:10.1111/j.1365-2966.2012.21833.x.
  6. 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, S2CID 118665352.
  7. "ome Ori". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-12-02.
  8. Hutter, D. J.; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hummel, C. A.; Zirm, H. (2021). "Surveying the Bright Stars by Optical Interferometry. III. A Magnitude-limited Multiplicity Survey of Classical Be Stars". The Astrophysical Journal Supplement Series. 257 (2): 69. arXiv:2109.06839. Bibcode:2021ApJS..257...69H. doi:10.3847/1538-4365/ac23cb. S2CID 237503492.
  9. Kaler, James B. (February 17, 2012), "Omega Orionis", Stars, University of Illinois, retrieved 2016-12-03.
  10. Balona, L. A.; Aerts, C.; Božić, H.; Guinan, E. F.; Handler, G.; James, D. J.; Kaye, A. B.; Shobbrook, R. R. (November 2001). "Short period line profile and light variations in the Be star ω Orionis". Monthly Notices of the Royal Astronomical Society. 327 (4): 1288–1296. Bibcode:2001MNRAS.327.1288B. doi:10.1046/j.1365-8711.2001.04831.x. S2CID 119578276.
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