Astronomy:12 Canis Majoris

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Short description: Variable star in the constellation Canis Major
12 Canis Majoris
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A visual band light curve for HK Canis Majoris (2020)[1]
Observation data
Equinox J2000.0]] (ICRS)
Constellation Canis Major
Right ascension  06h 47m 01.48353s[2]
Declination −21° 00′ 55.4517″[2]
Apparent magnitude (V) +6.07[3]
Characteristics
Spectral type B7 II/III[4] or B5 V[5]
B−V color index −0.159±0.004[3]
Variable type SX Ari[6]
Astrometry
Radial velocity (Rv)+16.4±2.5[3] km/s
Proper motion (μ) RA: −14.568[2] mas/yr
Dec.: +5.778[2] mas/yr
Parallax (π)4.6155 ± 0.0543 mas
Distance707 ± 8 ly
(217 ± 3 pc)
Absolute magnitude (MV)−0.81[3]
Details
Mass4.8[7] M☉
Radius2.73[8] R☉
Luminosity537[9] L☉
Surface gravity (log g)4.23[5] cgs
Temperature15,830±60[9] K
Metallicity [Fe/H]−0.37[10] dex
Rotation2.18045 d[7]
Rotational velocity (v sin i)65[7] km/s
Age134[11] Myr
Other designations
12 CMa, HK CMa, BD−20°1576, FK5 817, GC 8884, HD 49333, HIP 32504, HR 2509, SAO 172318[12]
Database references
SIMBADdata

12 Canis Majoris is a variable star located about 707 light years away from the Sun in the southern constellation of Canis Major.[12] It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07.[3] It is moving away from the Earth with a heliocentric radial velocity of +16 km/s.[3] This is the brightest star in the vicinity of the open cluster NGC 2287,[13] although it is probably not a member based on its proper motion.[14]

The Bayer designation ρ Canis Majoris/Rho Canis Majoris has been applied to this star in the past, but this is now rarely seen.[15] Perhaps the best-known use was by Charles Messier when describing the cluster Messier 41: "cluster of stars below Sirius, near Rho Canis Majoris".[16]

This star has a stellar classification of B7 II/III,[4] matching the spectrum of a B-type star intermediate between a giant and bright giant.[4] (Cidale et al. (2007) show a class of B5 V,[5] which would indicate it is instead a B-type main-sequence star.) It is a magnetic Bp star[17] of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere.[18]

Holger Pedersen and Bjarne Thomsen discovered that 12 Canis Majoris is a variable star, in 1977.[19] It was given its variable star designation in 1981.[20] Samus et al. (2017) classify it as an SX Arietis variable that varies in brightness by about 0.05 magnitudes over a period of 2.18045 days.[6] It has 4.8 times the mass of the Sun and 2.73[8] times the Sun's radius. The star is radiating 537 times the Sun's luminosity from its photosphere at an effective temperature of 15,830 K.

References

  1. ↑ Bernhard, Klaus; Hũmmerich, Stefan; Paunzen, Ernst (17 February 2020). "New and improved rotational periods of magnetic CP stars from ASAS-3, KELT, and MASCARA data". Monthly Notices of the Royal Astronomical Society 493 (3): 3293–3330. doi:10.1093/mnras/staa462. Bibcode: 2020MNRAS.493.3293B. 
  2. ↑ 2.0 2.1 2.2 2.3 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 3.4 3.5 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  4. ↑ 4.0 4.1 4.2 Houk, Nancy; Smith-Moore, M. (1978), Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode: 1988mcts.book.....H. 
  5. ↑ 5.0 5.1 5.2 Cidale, L. S. et al. (June 2007), "Fundamental parameters of He-weak and He-strong stars", Astronomy and Astrophysics 468 (1): 263–272, doi:10.1051/0004-6361:20066454, Bibcode: 2007A&A...468..263C. 
  6. ↑ 6.0 6.1 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. 
  7. ↑ 7.0 7.1 7.2 Shultz, M. E.; Owocki, S. P.; Ud-Doula, A.; Biswas, A.; Bohlender, D.; Chandra, P.; Das, B.; David-Uraz, A. et al. (2022). "MOBSTER - VI. The crucial influence of rotation on the radio magnetospheres of hot stars". Monthly Notices of the Royal Astronomical Society 513 (1): 1429. doi:10.1093/mnras/stac136. Bibcode: 2022MNRAS.513.1429S. 
  8. ↑ 8.0 8.1 Shulyak, D. et al. (2014), "Interferometry of chemically peculiar stars: Theoretical predictions versus modern observing facilities", Monthly Notices of the Royal Astronomical Society 443 (2): 1629, doi:10.1093/mnras/stu1259, Bibcode: 2014MNRAS.443.1629S. 
  9. ↑ 9.0 9.1 Netopil, M. et al. (November 2008), "Chemically peculiar stars and their temperature calibration", Astronomy and Astrophysics 491 (2): 545–554, doi:10.1051/0004-6361:200810325, Bibcode: 2008A&A...491..545N. 
  10. ↑ Mosser, B. et al. (February 2005), "Seismology and activity of the F type star HD 49933", Astronomy and Astrophysics 431 (2): L13–L16, doi:10.1051/0004-6361:200500003, Bibcode: 2005A&A...431L..13M. 
  11. ↑ Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters 38 (12): 771–782. doi:10.1134/S1063773712120031. ISSN 1063-7737. Bibcode: 2012AstL...38..771G. 
  12. ↑ 12.0 12.1 "12 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=12+CMa. 
  13. ↑ Feinstein, A. et al. (1979), "Multicolor photometry of the open cluster NGC 2287", International Astronomical Union, Reunion Astronomica Regional Latinoamericana, 1st, Santiago, Chile, Jan. 16-21, 1978, 3, Chile, Universidad: Departamento de Astronomia, Publicaciones, pp. 146–149, Bibcode: 1979rarl.conf..146F. 
  14. ↑ Levato, H.; Garcia, B. (1984), "Axial rotation in NGC 2287", Astrophysical Letters 24 (3): 161–164, Bibcode: 1984ApL....24..161L. 
  15. ↑ Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. p. 460. ISBN 978-0-939923-78-6. Bibcode: 2003lslm.book.....W. 
  16. ↑ Adam, Len (2018-04-04). Imaging the Messier Objects Remotely from Your Laptop. Springer. ISBN 978-3-319-65385-3. https://books.google.com/books?id=7nNUDwAAQBAJ&q=%2522rho%2520canis%2520majoris%2522&pg=PA202. Retrieved 2025-05-21. 
  17. ↑ Bailey, J. D.; Landstreet, J. D. (2013), "Abundances determined using Si ii and Si iii in B-type stars: Evidence for stratification", Astronomy & Astrophysics 551: A30, doi:10.1051/0004-6361/201220671, Bibcode: 2013A&A...551A..30B. 
  18. ↑ Farthmann, M. et al. (November 1994), "Stratification of helium in the photospheres of the helium-weak stars HD 28843 and HD 49333", Astronomy and Astrophysics 291: 919–927, Bibcode: 1994A&A...291..919F. 
  19. ↑ Pedersen, H.; Thomsen, B. (October 1977). "Spectrum and photometric variability of He-weak and He-strong stars". Astronomy and Astrophysics, Suppl. Ser. 30: 11–25. Bibcode: 1977A&AS...30...11P. https://articles.adsabs.harvard.edu/pdf/1977A%26AS...30...11P. Retrieved 1 January 2025. 
  20. ↑ Kholopov, P. N.; Samus, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (February 1981). "65th Name-List of Variable Stars". Information Bulletin on Variable Stars 1921: 1. Bibcode: 1981IBVS.1921....1K. https://ibvs.konkoly.hu/pub/ibvs/1901/1921.pdf. Retrieved 1 January 2025. 



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