Xi¹ Canis Majoris

Xi¹ Canis Majoris, Latinized from ξ¹ Canis Majoris, is a Beta Cephei variable star in the constellation Canis Major. It is approximately 1,400 light years from Earth.

For other star systems with this Bayer designation, see Xi Canis Majoris.

ξ¹ Canis Majoris

Location of ξ^1 Canis Majoris (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Canis Major
Right ascension	06^h 31^m 51.36636^s[1]
Declination	−23° 25′ 06.3181″[1]
Apparent magnitude (V)	4.33 - 4.36[2]
Characteristics
Spectral type	B1 III[3]
U−B color index	−0.98[4]
B−V color index	−0.24[4]
Variable type	β Cep[3]
Astrometry
Radial velocity (Rv)	+26.9[5] km/s
Proper motion (μ)	RA: −2.91[1] mas/yr Dec.: +6.22[1] mas/yr
Parallax (π)	2.36 ± 0.20[1] mas
Distance	1,400 ± 100 ly (420 ± 40 pc)
Absolute magnitude (MV)	−3.86[6]
Details
Mass	14.2±0.4[6] M☉
Radius	7.9±0.6[6] R☉
Luminosity	30900+8900 −6900[6] L☉
Surface gravity (log g)	3.78±0.07[6] cgs
Temperature	27000±1000[6] K
Metallicity [Fe/H]	−0.18[7] dex
Rotational velocity (v sin i)	0[6] km/s
Age	11.1±0.7[6] Myr
Other designations
ξ^1 CMa, 4 Canis Majoris, CD−23°3991, GC 8496, HD 46328, HIP 31125, HR 2387, SAO 171895, ADS 5176, CCDM 06319-2325
Database references
SIMBAD	data

ξ¹ Canis Majoris is a blue-white B-type star. It has generally been assigned a luminosity class of III (giant) or IV (subgiant), for example B1III[3] or B0.5IV.[6] Comparison of its properties with model evolutionary tracks suggest that it is a main sequence star about three quarters of the way through its main sequence lifetime.[6]

The apparent magnitude varies from +4.33 to +4.36 with a period of 5.03 hours.[2] Its pulsations cause its radius to vary by 1.0% to 1.5%. At the same time its effective temperature by about 500 K above and below its mean temperature.[6]

ξ¹ Canis Majoris has the longest known rotation period of any B class star, taking around 30 years to complete one revolution on its axis.[8] This is thought to be due to magnetic braking; ξ¹ Canis Majoris has the strongest magnetic field of any β Cephei star and would be expected to spin down completely in around four million years. It also has the strongest and hardest X-ray emission of any β Cephei star.[6]

ξ¹ Canis Majoris forms a naked eye pairing with ξ² Canis Majoris a little less than a degree away. The Washington Double Star Catalog lists two 14th magnitude companions about 27″ away.[9] In addition, an unseen close companion is suspected due to some faint emission lines in the spectrum that are best explained by a Be star invisible against the brighter primary.[6]

References

1. 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.
2. "International Variable Star Index". Retrieved 2018-11-13.
3. Hubrig, S.; et al. (January 2009). "New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars". Astronomische Nachrichten. 330 (4): 317. arXiv:0902.1314. Bibcode:2009AN....330..317H. doi:10.1002/asna.200811187.
4. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
5. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. Determination of Radial Velocities and Their Applications. 30. p. 57. Bibcode:1967IAUS...30...57E.
6. Shultz, M.; Wade, G. A.; Rivinius, Th.; Neiner, C.; Henrichs, H.; Marcolino, W.; MiMeS Collaboration (2017). "The pulsating magnetosphere of the extremely slowly rotating magnetic β Cep star ξ¹ CMa". Monthly Notices of the Royal Astronomical Society. 471 (2): 2286. Bibcode:2017MNRAS.471.2286S. doi:10.1093/mnras/stx1632.
7. 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.
8. Shultz, M.; Kochukhov, O.; Wade, G. A.; Rivinius, Th (2018). "The pulsationally modulated radial crossover signature of the slowly rotating magnetic B-type star ξ¹ CMa". Monthly Notices of the Royal Astronomical Society. 478 (1): L39. arXiv:1804.07535. Bibcode:2018MNRAS.478L..39S. doi:10.1093/mnrasl/sly070.
9. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.