Astronomy:Chi2 Orionis
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Orion |
| Right ascension | 06h 03m 55.18437s[1] |
| Declination | +20° 08′ 18.4281″[1] |
| Apparent magnitude (V) | 4.63[2][3] |
| Characteristics | |
| Spectral type | B2Ia[2] |
| U−B color index | −0.68[3] |
| B−V color index | +0.28[3] |
| R−I color index | +0.22[3] |
| Variable type | α Cyg[4] |
| Astrometry | |
| Radial velocity (Rv) | 16.8±0.9[5] km/s |
| Proper motion (μ) | RA: 2.679[1] mas/yr Dec.: −2.500[1] mas/yr |
| Parallax (π) | 0.7636 ± 0.1219[1] mas |
| Distance | approx. 4,300 ly (approx. 1,300 pc) |
| Absolute magnitude (MV) | −7.6[2] |
| Details | |
| Mass | 42.3±1.0[6] M☉ |
| Radius | 61.9[2] R☉ |
| Luminosity | 446,000[2] L☉ |
| Surface gravity (log g) | 2.35[2] cgs |
| Temperature | 19,000[2] K |
| Rotational velocity (v sin i) | 72[2] km/s |
| Age | 5±0.6[6] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Chi2 Orionis (Chi2 Ori / χ2 Orionis / χ2 Ori) /kaɪ.tuːˈɒraɪ/ is a B-type supergiant star in the constellation of Orion. It has an apparent visual magnitude of 4.63 but being quite distant, and heavily extinguished it burns with the greatest absolute visual light magnitude among stars in Orion within the near reaches of the galaxy, 0.9 of a magnitude brighter than Rigel.[citation needed] Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is considered to be a member of the Gemini OB1 association.[2]
In apparent brightness it ranks, within Orion, admitting the higher published mean brightness of much more variable stars ranked above it, 35th.[citation needed]
Chi1 Orionis is an unrelated, yellow, main sequence star over two degrees away.
Spectrum
χ2 Orionis has a B2 bright supergiant spectrum and is one of the standard B2 Ia stars.[7] It has been reported as having unusually narrow absorption lines and some weak emission lines and was included as one of the original Be stars.[8] It is no longer treated as a Be star since many supergiants show some emission features at high resolution and Be stars is usually defined to exclude supergiants.[9]
Variability
χ2 Orionis was listed as having likely small amplitude variability in photometry for the Third Catalogue of Stars measured in the Geneva Observatory Photometric System, specifically varying by 22 thousandths of a magnitude.[11] It was included in the General Catalogue of Variable Stars based on Hipparcos satellite photometry with a magnitude range (in the Hipparchos photometric system) of 4.68 - 4.72 and a period of 2.8 days.[12] A detailed study of the Hipparcos photometry confirmed the star as an α Cyg variable and gave the amplitude of variation as 0.057 magnitudes.[13]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 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.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Crowther, P. A.; Lennon, D. J.; Walborn, N. R. (2006). "Physical parameters and wind properties of galactic early B supergiants". Astronomy and Astrophysics 446: 279–293. doi:10.1051/0004-6361:20053685. Bibcode: 2006A&A...446..279C.
- ↑ 3.0 3.1 3.2 3.3 HR 2135, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line January 14, 2011.
- ↑ khi 2 Ori, database entry, The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars , Sternberg Astronomical Institute, Moscow, Russia. Accessed on line January 14, 2011.
- ↑ Wilson, Ralph Elmer (1953). General catalogue of stellar radial velocities. Carnegie Institution of Washington. Bibcode: 1953GCRV..C......0W.
- ↑ 6.0 6.1 Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society 410: 190–200. doi:10.1111/j.1365-2966.2010.17434.x. Bibcode: 2011MNRAS.410..190T.
- ↑ Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society 25: 1319, Bibcode: 1993AAS...183.1710G, http://www.astro.utoronto.ca/~garrison/mkstds.html, retrieved 2012-02-04
- ↑ Merrill, P. W.; Humason, M. L.; Burwell, C. G. (1925). "Discovery and Observations of Stars of Class Be". Astrophysical Journal 61: 389. doi:10.1086/142899. Bibcode: 1925ApJ....61..389M.
- ↑ Andrillat, Y.; Jaschek, M.; Jaschek, C. (1994). "A study of Be stars in the wavelength region around Paschen 7". Astronomy and Astrophysics Supplement Series 103. Bibcode: 1994A&AS..103..135A.
- ↑ "Light Curve". ESA. https://www.cosmos.esa.int/web/hipparcos/java-tools/light-curve.
- ↑ Rufener, F.; Bartholdi, P. (1982). "List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry". Astronomy and Astrophysics Supplement Series 48: 503. Bibcode: 1982A&AS...48..503R.
- ↑ Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars 4659: 1. Bibcode: 1999IBVS.4659....1K.
- ↑ Lefèvre, L.; Marchenko, S. V.; Moffat, A. F. J.; Acker, A. (2009). "A systematic study of variability among OB-stars based on HIPPARCOS photometry". Astronomy and Astrophysics 507 (2): 1141. doi:10.1051/0004-6361/200912304. Bibcode: 2009A&A...507.1141L.
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