ω Canis Majoris
Location of ω Canis Majoris (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Canis Major
Right ascension 07h 14m 48.65387s[1]
Declination −26° 46′ 21.6097″[1]
Apparent magnitude (V) 3.60 - 4.18[2]
Characteristics
Spectral type B2.5Ve[3]
U−B color index −0.73[4]
B−V color index −0.14[4]
Variable type γ Cas[2]
Astrometry
Proper motion (μ) RA: −11.88[1] mas/yr
Dec.: +6.87[1] mas/yr
Parallax (π)3.58 ± 0.17 mas[1]
Distance910 ± 40 ly
(280 ± 10 pc)
Absolute magnitude (MV)−3.21[5]
Details
Mass10.1±0.7[6] M☉
Radius6.2[7] R☉
Luminosity13,081[8] L☉
Surface gravity (log g)3.5[9] cgs
Temperature21,878[9] K
Rotational velocity (v sin i)80[10] km/s
Age22.5±2.6[6] Myr
Other designations
ω CMa, 28 Canis Majoris, CD−26°4073, GC 9625, HD 56139, HIP 35037, HR 2749, SAO 173282[11]
Database references
SIMBADdata

Omega Canis Majoris, Latinized from ω Canis Majoris, is a solitary,[12] blue-white-hued star in the equatorial constellation of Canis Major. It is visible to the naked eye with an apparent visual magnitude of about 4. Based upon an annual parallax shift of just 3.58 mas as seen from Earth,[1] this system is located roughly 910 light-years from the Sun.

A visual band light curve for Omega Canis Majoris, adapted from Štefl et al. (2003)[13]

This star has a stellar classification of B2.5Ve, indicating it is a main sequence Be star, although it has also been classified as a subgiant.[14] One of the most observed Be stars of the Southern Hemisphere,[15] Omega Canis Majoris is classified as a Gamma Cassiopeiae-type variable star.[2] Both the luminosity and the radial velocity vary with a primary cyclical period of 1.372 days.[16] The variation in brightness, ranging from magnitude +3.60 to +4.18,[2] shows changes over time, which suggests there are two overlapping periods of 1.37 and 1.49 days. The star also undergoes transient periodicities following outbursts.[17][10]

This is a massive star with ten[6] times the mass of the Sun and 6.2[7] times the Sun's radius. At an estimated age of 22.5 million years,[6] it is radiating 13,081[8] times the Sun's luminosity from its photosphere at an effective temperature of 21,878 K.[9] The star is being viewed nearly pole on, so the measured projected rotational velocity of 80 km/s is only a fraction of the true equatorial velocity, estimated as 350 km/s. It is surrounded by a symmetric circumstellar decretion disk of material that is being heated by the star, which in turn is inserting emission lines into the combined spectrum.[10]

References

  1. 1 2 3 4 5 6 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. 1 2 3 4 Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  3. ↑ Slettebak, A. (1982), "Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars", Astrophysical Journal Supplement Series, 50: 55–83, Bibcode:1982ApJS...50...55S, doi:10.1086/190820, 80.
  4. 1 2 Feinstein, A.; Marraco, H. G. (November 1979), "The photometric behavior of Be Stars", Astronomical Journal, 84: 1713–1725, Bibcode:1979AJ.....84.1713F, doi:10.1086/112600.
  5. ↑ 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.
  6. 1 2 3 4 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.
  7. 1 2 Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
  8. 1 2 Hohle, M. M.; et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
  9. 1 2 3 Soubiran, C.; et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
  10. 1 2 3 Stefl, S.; et al. (February 2010), "The 2008+ outburst of the Be star 28 CMa", in Rivinius, Th.; Curé, M. (eds.), The Interferometric View on Hot Stars, Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias, vol. 38, pp. 89–91, Bibcode:2010RMxAC..38...89S.
  11. ↑ "ome CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-09-03.
  12. ↑ 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.
  13. ↑ Štefl, S.; Baade, D.; Rivinius, Th.; Otero, S.; Stahl, O.; Budovičová, A.; Kaufer, A.; Maintz, M. (April 2003). "Stellar and circumstellar activity of the Be star ω CMa I. Line and continuum emission in 1996–2002" (PDF). Astronomy and Astrophysics. 402: 253–265. Bibcode:2003A&A...402..253S. doi:10.1051/0004-6361:20030224. Retrieved 31 July 2022.
  14. ↑ Skiff, B. A. (October 2014), "Catalogue of Stellar Spectral Classifications", Lowell Observatory, VizieR On-line Data Catalog: B/mk, Bibcode:2014yCat....1.2023S.
  15. ↑ Ghoreyshi, M. R.; et al. (November 2016), "Modeling the Complete Lightcurve of ω CMa", in Sigut, T. A. A.; Jones, C. E. (eds.), Bright Emissaries: Be Stars as Messengers of Star-Disk Physics, Proceedings of a Meeting held at The University of Western Ontario, in London, Ontario, Canada, 11-13 August 2014, vol. 506, San Francisco: Astronomical Society of the Pacific, p. 315, arXiv:1506.08902, Bibcode:2016ASPC..506..315G.
  16. ↑ Harmanec, P. (June 1998), "On the nature of the Be phenomenon. I. The case of omega Canis Majoris", Astronomy and Astrophysics, 334: 558–570, Bibcode:1998A&A...334..558H.
  17. ↑ Štefl, S.; et al. (2000), "Tracing the Transient Periods in the Be Star 28 ω CMa", in Smith, Myron A.; Henrichs, Huib F. (eds.), The Be Phenomenon in Early-Type Stars, IAU Colloquium 175, ASP Conference Proceedings, vol. 214, Astronomical Society of the Pacific, p. 240, Bibcode:2000ASPC..214..240S, ISBN 1-58381-045-5.
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