12 Canis Majoris

12 Canis Majoris is a variable star located 750 light years away from the Sun[2] 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]

12 Canis Majoris

A visual band light curve for HK Canis Majoris (2020)[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Major
Right ascension 06h 47m 01.48373s[2]
Declination −21° 00′ 55.4494″[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: −14.53[7] mas/yr
Dec.: +5.12[7] mas/yr
Parallax (π)4.3273 ± 0.0824 mas
Distance750 ± 10 ly
(231 ± 4 pc)
Absolute magnitude (MV)−0.81[3]
Details
Mass1.25[8] M☉
Radius2.73[9] R☉
Luminosity497.88[3] L☉
Surface gravity (log g)4.23[5] cgs
Temperature15,830±60[10] K
Metallicity [Fe/H]−0.37[11] dex
Rotation2.18045 d[6]
Rotational velocity (v sin i)9.5±0.3 km/s
Other designations
12 Cep, HK CMa, BD−20°1576, FK5 817, GC 8884, HD 49333, HIP 32504, HR 2509, SAO 172318[12]
Database references
SIMBADdata

This star has a stellar classification of B7 II/III,[4] matching a B-type giant/bright giant hybrid.[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[15] of the helium–weak variety (CP4), with the spectrum displaying evidence for vertical stratification of helium in the atmosphere.[16] 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 1.25[8] times the mass of the Sun and 2.73[9] times the Sun's radius. The star is radiating 498[3] times the Sun's luminosity from its photosphere at an effective temperature of 6,500 K.[11]

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. Retrieved 15 November 2021.
  2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. 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.
  4. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  5. Cidale, L. S.; et al. (June 2007), "Fundamental parameters of He-weak and He-strong stars", Astronomy and Astrophysics, 468 (1): 263–272, arXiv:0705.0541, Bibcode:2007A&A...468..263C, doi:10.1051/0004-6361:20066454, S2CID 14143604.
  6. 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.
  7. 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.
  8. Goupil, M. J.; et al. (November 2006), "Rotational Splittings with CoRoT, Expected Number of Detections and Measurement Accuracy", in Fridlund, M.; Baglin, A.; Lochard, J.; Conroy, L. (eds.), Proceedings of "The CoRoT Mission Pre-Launch Status - Stellar Seismology and Planet Finding" (ESA SP-1306), vol. 1306, p. 453, Bibcode:2006ESASP1306..453G, ISBN 92-9092-465-9.
  9. 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, arXiv:1406.6093, Bibcode:2014MNRAS.443.1629S, doi:10.1093/mnras/stu1259, S2CID 96452769.
  10. Netopil, M.; et al. (November 2008), "Chemically peculiar stars and their temperature calibration", Astronomy and Astrophysics, 491 (2): 545–554, arXiv:0809.5131, Bibcode:2008A&A...491..545N, doi:10.1051/0004-6361:200810325, S2CID 14084961.
  11. Mosser, B.; et al. (February 2005), "Seismology and activity of the F type star HD 49933", Astronomy and Astrophysics, 431: L13–L16, arXiv:astro-ph/0501459, Bibcode:2005A&A...431L..13M, doi:10.1051/0004-6361:200500003, S2CID 18412104.
  12. "12 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 30, 2019.
  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, vol. 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. 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, arXiv:1301.3050, Bibcode:2013A&A...551A..30B, doi:10.1051/0004-6361/201220671, S2CID 59291051.
  16. 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.
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