27 Canis Majoris

Blue band light curves for EW Canis Majoris. The main plot shows the long term variability, and the inset plot shows the short term variability. Adapted from Mennickent et al. (1994) and Balona & Rozowsky (1991).[1][2]
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension 07h 14m 15.21192s[3]
Declination −26° 21′ 09.0312″[3]
Apparent magnitude (V) +4.65[4] (+4.92 + 5.39)[5]
Characteristics
Spectral type B3 IIIpe[6]
B−V color index −0.17±0.16[7]
Variable type γ Cas + β Cep:[8]
Astrometry
Radial velocity (Rv)16.3±3.6[7] km/s
Proper motion (μ) RA: −6.91[3] mas/yr
Dec.: +3.17[3] mas/yr
Parallax (π)1.88 ± 0.32 mas[3]
Distanceapprox. 1,700 ly
(approx. 530 pc)
Absolute magnitude (MV)−4.13[7]
Orbit[9]
Period (P)118.54±11.14 yr
Semi-major axis (a)0.178±0.012″
Eccentricity (e)0.747±0.094
Inclination (i)80.2±1.0°
Longitude of the node (Ω)131.3±3.0°
Periastron epoch (T)1,971.01±0.74
Argument of periastron (ω)
(secondary)		85.0±3.6°
Details
27 CMa A
Mass12.5±2.5[10] M☉
Luminosity (bolometric)15,610[4] L☉
Surface gravity (log g)3.514[11] cgs
Temperature21,061[11] K
Rotational velocity (v sin i)290[11] km/s
Age0.1±0.1[10] Myr
Other designations
27 CMa, EW Canis Majoris, BD−26°4057, GC 9608, HD 56014, HIP 34981, HR 2745, SAO 173264, CCDM J07143-2621, WDS J07143-2621[12]
Database references
SIMBADdata

27 Canis Majoris is a binary star[5] system in the northern constellation of Canis Major,[12] located approximately 1,700 light years away from the Sun.[3] It has the variable star designation EW Canis Majoris;[8] 27 Canis Majoris is the Flamsteed designation. This system is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude of +4.65.[4] It is moving away from the Earth with a heliocentric radial velocity of 16 km/s.[7]

The pair of stars in this system were first resolved by W. S. Finsen in 1953, and the split has been widening since that time.[13] The system has an orbital period of around 119 years with an eccentricity of 0.7 and a semimajor axis of 0.178″.[9] The magnitude 4.92[5] primary, designated component A, is a Be star with a stellar classification of B3 IIIpe.[6] It is spinning rapidly with a projected rotational velocity of 290 km/s, compared to a critical velocity of 389 km/s.[11] The star appears to be a Beta Cephei variable[14] with a pulsation period of 0.0919 days and an amplitude of 0.0080 in magnitude.[15]

The magnitude 5.39[5] secondary, component B, is classified as a Gamma Cassiopeiae type variable star. Due to its variable nature, the brightness of the system varies from magnitude +4.42 to +4.82.[8]

References

  1. ^ Mennickent, R. E.; Vogt, N.; Sterken, C. (November 1994). "Long-term photometry of Be stars. I. Fading events and variations on time scales of years". Astronomy & Astrophysics Supplement Series. 108: 237–250. Bibcode:1994A&AS..108..237M.
  2. ^ Balona, Luis A.; Rozowsky, Joel (August 1991). "Appearance of beta cephei pulsations in the Be star 27 CMa". Monthly Notices of the Royal Astronomical Society. 251: 66–68. Bibcode:1991MNRAS.251P..66B. doi:10.1093/mnras/251.1.66P.
  3. ^ a b c d e f 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.
  4. ^ a b c 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.
  5. ^ a b c d 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.
  6. ^ a b Woods, M. L. (1958), "Spectral types of bright southern stars", Memoirs of the Mount Stromlo Observatory, 12: 125, Bibcode:1955MmMtS..12..125W.
  7. ^ a b c d 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.
  8. ^ a b c 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.
  9. ^ a b Hartkopf, W. I.; et al. (June 30, 2006), Sixth Catalog of Orbits of Visual Binary Stars, United States Naval Observatory, archived from the original on 2017-04-30, retrieved 2017-06-02.
  10. ^ a b 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.
  11. ^ a b c d Frémat, Y.; Zorec, J.; Hubert, A.-M.; Floquet, M. (2005), "Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars", Astronomy and Astrophysics, 440 (1): 305, arXiv:astro-ph/0503381, Bibcode:2005A&A...440..305F, doi:10.1051/0004-6361:20042229, S2CID 19016751.
  12. ^ a b "27 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 1, 2019.
  13. ^ Mason, Brian D.; et al. (November 1997), "ICCD Speckle Observations of Binary Stars. XVIII. An Investigation of Be Stars", Astronomical Journal, 114: 2112, Bibcode:1997AJ....114.2112M, doi:10.1086/118630.
  14. ^ Balona, L. A.; Krisciunas, K. (May 1994), "Further Confirmation that the Be Star 27 CMa is a beta Cep Variable", Information Bulletin on Variable Stars, 4022 (4022): 1, Bibcode:1994IBVS.4022....1B.
  15. ^ Stankov, Anamarija; Handler, Gerald (2005), "Catalog of Galactic β Cephei Stars", The Astrophysical Journal Supplement Series, 158 (2): 193–216, arXiv:astro-ph/0506495, Bibcode:2005ApJS..158..193S, doi:10.1086/429408, ISSN 0067-0049, S2CID 119526948.
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