(Redirected from Chi_Oph)
Chi Ophiuchi, Latinized from χ Ophiuchi, is a variable star in the equatorial constellation of Ophiuchus. It has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.22. The distance to this object, as determined from parallax measurements, is approximately 530 light years, but it is moving closer to the Sun with a radial velocity of −19 km/s. This star is a proper motion member of the Upper Scorpius sub-group in the Scorpius-Centaurus OB association; the nearest such co-moving association of massive stars to the Sun.
Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||16h 27m 01.43499s|
|Declination||−18° 27′ 22.4938″|
|Apparent magnitude (V)||4.22 (4.18 to 5.0)|
|Evolutionary stage||main sequence|
|U−B color index||−0.75|
|B−V color index||+0.28|
|R−I color index||+0.22|
|Variable type||GCAS + LERI|
|Radial velocity (Rv)||−19.0±2.1 km/s|
|Proper motion (μ)|| RA: −5.41 mas/yr |
Dec.: −21.12 mas/yr
|Parallax (π)||6.21 ± 0.23 mas|
|Distance||530 ± 20 ly |
(161 ± 6 pc)
|Absolute magnitude (MV)||−4.6|
|Surface gravity (log g)||4.13 cgs|
|Rotational velocity (v sin i)||134 km/s|
This is a massive Be star with a stellar classification of B2Vne, where the 'n' indicates "nebulous" lines due to rapid rotation. It is spinning with a projected rotational velocity of 144 km/s. As the critical velocity for the star is 477 km/s, the inclination angle of its poles must be small; estimated as ~20°. It is a Gamma Cassiopeiae variable with an amplitude of 0.15 magnitude. The brightness has been measured varying from magnitude 4.18 down to 5.0.
Chi Ophiuchi is 22.5 million years old with 10.1 times the mass of the Sun. It has 12.6 times the Sun's radius and is radiating 245 times the luminosity of the Sun from its photosphere at an effective temperature of 6,432 K. A weak magnetic field has been detected in the chromosphere of this star. It is being orbited by a symmetrical disk of ejected gas extending out to 0.52 AU (112 R☉), and excess radio and infrared emission has been detected from this structure.
Abt and Levy (1978) cataloged Chi Ophiuchi as a single-lined spectroscopic binary with a period of 138.8 days and an eccentricity of 0.44, although the orbital elements are considered marginal. Eggleton and Tokovinin (2008) list it as a single star.
- ^ a b c d e f 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 .
- ^ a b 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 .
- ^ a b c Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S . doi:10.1134/S1063772917010085 . S2CID 125853869 . Note: cataloged as 'ksi Oph'.
- ^ a b Houk, Nancy; Smith-Moore, M. (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. 4. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode:1988mcts.book.....H .
- ^ a b c d Hoffleit, D.; Warren, Jr., W. H. "The Bright Star Catalogue" (5th Revised ed.). CDS. Retrieved 2019-10-24. HR 6118 , database entry.
- ^ Watson, C. L. (2006). "The International Variable Star Index (VSX)". The Society for Astronomical Sciences 25th Annual Symposium on Telescope Science. Held May 23–25. 25: 47. Bibcode:2006SASS...25...47W .
- ^ a b Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053 . Bibcode:2006AstL...32..759G . doi:10.1134/S1063773706110065 . S2CID 119231169 .
- ^ a b c de Geus, E. J.; et al. (June 1989). "Physical parameters of stars in the Scorpio-Centaurus OB association". Astronomy and Astrophysics. 216 (1–2): 44–61. Bibcode:1989A&A...216...44D .
- ^ a b c d Tetzlaff, N.; et al. (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 .
- ^ a b c d e f 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.
- ^ a b "chi Oph" . SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved January 12, 2011.
- ^ a b Tycner, C.; et al. (December 2008). "Constraining the Physical Parameters of the Circumstellar Disk of χ Ophiuchi". The Astrophysical Journal. 689 (1): 461–470. arXiv:0807.3971 . Bibcode:2008ApJ...689..461T . doi:10.1086/592097 . S2CID 16779318 .
- ^ Adelman, S. J.; et al. (December 2000). "On the Variability of O4-B5 Luminosity Class III-V Stars". Information Bulletin on Variable Stars. 5008: 1. Bibcode:2000IBVS.5008....1A .
- ^ Hubrig, S.; et al. (December 2007). "Evidence for weak magnetic fields in early-type emission stars". Astronomische Nachrichten. 328 (10): 1133. arXiv:0711.2085 . Bibcode:2007AN....328.1133H . doi:10.1002/asna.200710877 . S2CID 15213781 .
- ^ Taylor, A. R.; et al. (October 1987). "Radio detection of the Be star psi Persei" . Monthly Notices of the Royal Astronomical Society. 228 (4): 811–817. Bibcode:1987MNRAS.228..811T . doi:10.1093/mnras/228.4.811 .
- ^ Abt, H. A.; Levy, S. G. (February 1978). "Binaries among B2 - B5 IV, V absorption and emission stars". Astrophysical Journal Supplement Series. 36: 241–258. Bibcode:1978ApJS...36..241A . doi:10.1086/190498 .
- ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878 . Bibcode:2008MNRAS.389..869E . doi:10.1111/j.1365-2966.2008.13596.x . S2CID 14878976 .
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