26 Canis Majoris

26 Canis Majoris is a variable star in the southern constellation of Canis Major,^[10] located around 1,010 light years away from the Sun.^[2] It has the variable star designation MM Canis Majoris; 26 Canis Majoris is the Flamsteed designation.^[10] This object is visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of 5.89.^[3] It is moving further from the Earth with a heliocentric radial velocity of +22 km/s.^[6]

26 Canis Majoris

A light curve for MM Canis Majoris from Hipparcos data, adapted from Aerts et al. (1999)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Canis Major
Right ascension	07h 12m 12.21483s[2]
Declination	−25° 56′ 33.3107″[2]
Apparent magnitude (V)	5.89[3] or (5.84 – 5.87)[4]
Characteristics
Spectral type	B2 IV/V[5]
B−V color index	−0.170±0.004[6]
Variable type	SPB[4]
Astrometry
Radial velocity (Rv)	+21.6±2.9[6] km/s
Proper motion (μ)	RA: −5.678[2] mas/yr Dec.: +8.929[2] mas/yr
Parallax (π)	3.2442 ± 0.0841 mas[2]
Distance	1,010 ± 30 ly (308 ± 8 pc)
Absolute magnitude (MV)	−1.11[6]
Details
Mass	5.5±0.9[7] M☉
Radius	3.25[3] R☉
Luminosity	1,000+995 −499[7] L☉
Surface gravity (log g)	3.777±0.027[8] cgs
Temperature	16,157±200[8] K
Rotation	2.729±0.001[7]
Rotational velocity (v sin i)	64±14[8] km/s
Age	3.6±3.3[9] Myr
Other designations
26 CMa, MM CMa, BD−25°4191, GC 9545, HD 55522, HIP 34798, HR 2718, SAO 173193[10]
Database references
SIMBAD	data

With a stellar classification of B2 IV/V,^[5] it appears as a B-type main-sequence star intermixed with traits of an evolving subgiant star. Samus et al. (2017) classify it as a slowly pulsating B-type variable star (SPB), which ranges from magnitude 5.84 down to 5.87 with a rotationally-modulated period of 2.72945 days.^[4] Briquet et al. (2007) describe it as a chemically peculiar He-variable star, having inhomogeneous distributions of chemical elements across its surface. It has a variable, quasi-dipolar magnetic field, resulting in variations of the magnetic field and line strengths as it rotates.^[7]

This star is around 3.6^[9] million years old with a rotation period of 2.7 days.^[7] It has 5.5^[7] times the mass of the Sun and 3.25^[3] times the Sun's radius. The star is radiating 1,000^[7] times as much luminosity as the Sun from its photosphere at an effective temperature of 16,157 K.^[8]

References

1. Aerts, C.; De Cat, P.; Peeters, E.; Decin, L.; De Ridder, J.; Kolenberg, K.; Meeus, G.; Van Winckel, H.; Cuypers, J.; Waelkens, C. (March 1999). "Selection of a sample of bright southern Slowly Pulsating B Stars for long-term photometric and spectroscopic monitoring". Astronomy & Astrophysics. 343: 872–882. Bibcode:1999A&A...343..872A. 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. 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.
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.
5. 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.
6. 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.
7. Briquet, M.; et al. (January 2007), "Discovery of magnetic fields in three He variable Bp stars with He and Si spots", Astronomische Nachrichten, 328 (1): 41–45, arXiv:astro-ph/0610537, Bibcode:2007AN....328...41B, doi:10.1002/asna.200610702, S2CID 18724568.
8. Huang, W.; et al. (2010), "A Stellar Rotation Census of B Stars: From ZAMS to TAMS", The Astrophysical Journal, 722 (1): 605–619, arXiv:1008.1761, Bibcode:2010ApJ...722..605H, doi:10.1088/0004-637X/722/1/605, S2CID 118532653.
9. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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.
10. "26 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved May 1, 2019.