Astronomy:Xi1 Canis Majoris
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Canis Major[1] |
| Right ascension | 06h 31m 51.366s[2] |
| Declination | −23° 25′ 06.32″[2] |
| Apparent magnitude (V) | 4.33 to 4.36[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4] |
| Spectral type | B1III[5] or B0.7IV[6] |
| U−B color index | −0.98[7] |
| B−V color index | −0.24[7] |
| Variable type | β Cep[5] |
| Astrometry | |
| Radial velocity (Rv) | +26.9[8] km/s |
| Proper motion (μ) | RA: −3.352[2] mas/yr Dec.: +6.157[2] mas/yr |
| Parallax (π) | 2.1660 ± 0.1257[2] mas |
| Distance | 1,510 ± 90 ly (460 ± 30 pc) |
| Absolute magnitude (MV) | −3.86[4] |
| Details | |
| Mass | 14.2±0.4[4] M☉ |
| Radius | 7.9±0.6[4] R☉ |
| Luminosity | 30,900+8,900 −6,900[4] L☉ |
| Surface gravity (log g) | 3.78±0.07[4] cgs |
| Temperature | 27,000±1,000[4] K |
| Metallicity [Fe/H] | −0.18[1] dex |
| Rotational velocity (v sin i) | 0[4] km/s |
| Age | 11.1±0.7[4] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Xi1 Canis Majoris is a blue-white variable star in the constellation Canis Major. Its name is a Bayer designation that is Latinized from ξ1 Canis Majoris, and abbreviated Xi1 CMa or ξ1 CMa. This star is visible to the naked eye with an apparent visual magnitude of +4.3.[3] Based on an annual parallax shift of 2.17 mas,[2] it is located at a distance of approximately 1,510 light-years (460 pc) from Earth.
Properties
The stellar classification of Xi1 Canis Majoris matches an early-type B-type star. It has generally been assigned a luminosity class of III (giant) or IV (subgiant), for example B1III[5] or B0.5IV.[4][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.[4] Its estimated age is 11 million years.[4] This is a massive star with 14 times the mass of the Sun and 8 times the Sun's radius.[4] It is radiating 30,900[4] times the luminosity of the Sun from its photosphere at an effective temperature of 27,000 K.[4]
ξ1 Canis Majoris is classified as a Beta (β) Cephei variable that ranges from magnitude +4.33 to +4.36 with a period of 5.03 hours.[3] This period has remained very stable, changing by no more than one second per century.[11] Its pulsations cause its radius to vary by 1.0% to 1.5%. At the same time its effective temperature varies by about 500 K above and below its mean temperature.[4]
It has the longest known rotation period of any B class star, taking around 30 years to complete one revolution on its axis.[12] 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.[4] The X-ray emission varies in phase with the optical pulsations. The stellar wind from ξ1 Canis Majoris is very weak with a terminal velocity of 700 km/s; the star is losing less than 10−10 M☉·yr−1.[11]
This star 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 at an angular separation of about 27″.[13] 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 that is invisible against the brighter primary.[4]
References
- ↑ 1.0 1.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 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.
- ↑ 3.0 3.1 3.2 "International Variable Star Index". American Association of Variable Star Observers. https://www.aavso.org/vsx/index.php?view=detail.top&oid=5509.
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 Shultz, M. et al. (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. doi:10.1093/mnras/stx1632. Bibcode: 2017MNRAS.471.2286S.
- ↑ 5.0 5.1 5.2 Hubrig, S. et al. (January 2009). "New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars". Astronomische Nachrichten 330 (4): 317. doi:10.1002/asna.200811187. Bibcode: 2009AN....330..317H.
- ↑ 6.0 6.1 Negueruela, I. et al. (2024). "The IACOB project: XII. New grid of northern standards for the spectral classification of B-type stars". Astronomy and Astrophysics 690: id. A176. doi:10.1051/0004-6361/202449298. Bibcode: 2024A&A...690A.176N.
- ↑ 7.0 7.1 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.
- ↑ Evans, D. S. (June 20–24, 1966). "Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30". in Batten, Alan Henry; Heard, John Frederick. 30. 57. Bibcode: 1967IAUS...30...57E.
- ↑ "ksi01 CMa". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=ksi01+CMa.
- ↑ "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html.
- ↑ 11.0 11.1 Oskinova, Lidia M. et al. (June 2014). "Discovery of X-ray pulsations from a massive star". Nature Communications 5: id. 4024. doi:10.1038/ncomms5024. Bibcode: 2014NatCo...5.4024O.
- ↑ Shultz, M. et al. (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. doi:10.1093/mnrasl/sly070. Bibcode: 2018MNRAS.478L..39S.
- ↑ Mason, Brian D. et al. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M.
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