Astronomy:Omega Canis Majoris

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Short description: Star in the constellation Canis Major
ω Canis Majoris
Location of ω Canis Majoris (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Canis Major[1]
Right ascension  07h 14m 48.654s[2]
Declination −26° 46′ 21.60″[2]
Apparent magnitude (V) 3.60 to 4.18[3]
Characteristics
Spectral type B2.5Ve[4]
U−B color index −0.73[5]
B−V color index −0.14[5]
Variable type γ Cas[3]
Astrometry
Radial velocity (Rv)23.2±2.4[6] km/s
Proper motion (μ) RA: −11.617[2] mas/yr
Dec.: +8.109[2] mas/yr
Parallax (π)3.5610 ± 0.1524[2] mas
Distance920 ± 40 ly
(280 ± 10 pc)
Absolute magnitude (MV)−3.21[1]
Details
Mass10.1±0.7[7] M☉
Radius6.2[8] R☉
Luminosity13,081[9] L☉
Surface gravity (log g)3.5[10] cgs
Temperature21,878[10] K
Rotational velocity (v sin i)80[11] km/s
Age22.5±2.6[7] Myr
Other designations
ω CMa, 28 Canis Majoris, CD−26°4073, GC 9625, HD 56139, HIP 35037, HR 2749, SAO 173282[12]
Database references
SIMBADdata

Omega Canis Majoris is a solitary,[13] blue-white-hued star in the equatorial constellation of Canis Major. Its name is a Bayer designation that is Latinized from ω Canis Majoris, and abbreviated Omega CMa or ω CMa. This star is visible to the naked eye with an apparent visual magnitude of about 4. Based upon an annual parallax shift of 3.56 mas as seen from Earth,[2] this system is located roughly 920 light-years (280 pc) away from the Sun. It is drifting further away with a line of sight velocity of 23 km/s.[6]

Properties

A visual band light curve for Omega Canis Majoris, adapted from Štefl et al. (2003)[14]

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.[15] One of the most observed Be stars of the Southern Hemisphere,[16] Omega Canis Majoris is classified as a Gamma Cassiopeiae-type variable star.[3] Both the luminosity and the radial velocity vary with a primary cyclical period of 1.372 days.[17] The variation in brightness, ranging from magnitude +3.60 to +4.18,[3] 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.[18][11]

This is a massive star with ten[7] times the mass of the Sun and 6.2[8] times the Sun's radius. At an estimated age of 22.5 million years,[7] it is radiating 13,081[9] times the Sun's luminosity from its photosphere at an effective temperature of 21,878 K.[10] 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.[11]

References

  1. ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940.  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 Samus, N. N. et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1 61 (1): 80–88, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  4. ↑ 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, doi:10.1086/190820, 80, Bibcode: 1982ApJS...50...55S. 
  5. ↑ 5.0 5.1 Feinstein, A.; Marraco, H. G. (November 1979), "The photometric behavior of Be Stars", Astronomical Journal 84: 1713–1725, doi:10.1086/112600, Bibcode: 1979AJ.....84.1713F. 
  6. ↑ 6.0 6.1 Gontcharov, G. A. (2006), "Pulkovo compilation of radial velocities for 35495 stars in a common system", Astronomy Letters 32 (11): 759–771, doi:10.1134/S1063773706110065, Bibcode: 2006AstL...32..759G. 
  7. ↑ 7.0 7.1 7.2 7.3 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T. 
  8. ↑ 8.0 8.1 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, doi:10.1093/mnras/189.3.601, Bibcode: 1979MNRAS.189..601U 
  9. ↑ 9.0 9.1 Hohle, M. M. et al. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten 331 (4): 349, doi:10.1002/asna.200911355, Bibcode: 2010AN....331..349H. 
  10. ↑ 10.0 10.1 10.2 Soubiran, C. et al. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics 515: A111, doi:10.1051/0004-6361/201014247, Bibcode: 2010A&A...515A.111S. 
  11. ↑ 11.0 11.1 11.2 Stefl, S. et al. (February 2010), "The 2008+ outburst of the Be star 28 CMa", in Rivinius, Th.; Curé, M., The Interferometric View on Hot Stars, Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias, 38, pp. 89–91, Bibcode: 2010RMxAC..38...89S. 
  12. ↑ "ome CMa". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ome+CMa. 
  13. ↑ 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, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E. 
  14. ↑ Štefl, S. et al. (April 2003). "Stellar and circumstellar activity of the Be star ω CMa I. Line and continuum emission in 1996–2002". Astronomy and Astrophysics 402: 253–265. doi:10.1051/0004-6361:20030224. Bibcode: 2003A&A...402..253S. https://www.aanda.org/articles/aa/pdf/2003/16/aa3203.pdf. Retrieved 31 July 2022. 
  15. ↑ Skiff, B. A. (October 2014), "Catalogue of Stellar Spectral Classifications", Lowell Observatory, VizieR On-line Data Catalog: B/mk, Bibcode: 2014yCat....1.2023S. 
  16. ↑ Ghoreyshi, M. R. et al. (November 2016), "Modeling the Complete Lightcurve of ω CMa", in Sigut, T. A. A.; Jones, C. E., 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, 506, San Francisco: Astronomical Society of the Pacific, p. 315, Bibcode: 2016ASPC..506..315G. 
  17. ↑ 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. 
  18. ↑ Štefl, S. et al. (2000), "Tracing the Transient Periods in the Be Star 28 ω CMa", in Smith, Myron A.; Henrichs, Huib F., The Be Phenomenon in Early-Type Stars, IAU Colloquium 175, ASP Conference Proceedings, 214, Astronomical Society of the Pacific, p. 240, ISBN 1-58381-045-5, Bibcode: 2000ASPC..214..240S. 



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