Sigma Orionis

σ Orionis
Location of σ Ori (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 38m 42.0s[1]
Declination −2° 36′ 00″[1]
Apparent magnitude (V) A: 4.07[2]
B: 5.27
C: 8.79
D: 6.62
E: 6.66 (6.61 - 6.77[3])
Characteristics
AB
Spectral type O9.5V + B0.5V[4]
U−B color index −1.02[5]
B−V color index −0.31[5]
C
Spectral type A2 V[6]
U−B color index −0.25[7]
B−V color index −0.02[7]
D
Spectral type B2 V[6]
U−B color index −0.87[8]
B−V color index −0.17[8]
E
Spectral type B2 Vpe[9]
U−B color index −0.84[10]
B−V color index −0.09[10]
Variable type SX Ari[3]
Astrometry
Radial velocity (Rv)−29.45 ± 0.45[11] km/s
Parallax (π)AB: 3.04 ± 8.92[12] mas
D: 6.38 ± 0.90 mas[12]
Distance387.51 ± 1.32[13] pc
Absolute magnitude (MV)−3.49 (Aa)
−2.90 (Ab)
−2.79 (B)[14]
Orbit[13]
PrimaryAa
CompanionAb
Period (P)143.2002 ± 0.0024 days
Semi-major axis (a)0.0042860"
(~360 R☉[15])
Eccentricity (e)0.77896 ± 0.00043
Inclination (i)~56.378 ± 0.085°
Semi-amplitude (K1)
(primary)		72.03 ± 0.25 km/s
Semi-amplitude (K2)
(secondary)		95.53 ± 0.22 km/s
Orbit[13]
PrimaryA
CompanionB
Period (P)159.896 ± 0.005 yr
Semi-major axis (a)0.2629 ± 0.0022″
Eccentricity (e)0.024 ± 0.005
Inclination (i)172.1 ± 4.6°
Details[14]
σ Ori Aa
Mass18 M☉
Radius5.6 R☉
Luminosity41,700 L☉
Surface gravity (log g)4.20 cgs
Temperature35,000 K
Rotational velocity (v sin i)135 km/s
Age0.3 Myr
σ Ori Ab
Mass13 M☉
Radius4.8 R☉
Luminosity18,600 L☉
Surface gravity (log g)4.20 cgs
Temperature31,000 K
Rotational velocity (v sin i)35 km/s
Age0.9 Myr
σ Ori B
Mass14 M☉
Radius5.0 R☉
Luminosity15,800 L☉
Surface gravity (log g)4.15 cgs
Temperature29,000 K
Rotational velocity (v sin i)250 km/s
Age1.9 Myr
Details[6]
C
Mass2.7 M☉
Details[16]
D
Mass6.8 M☉
Surface gravity (log g)4.3 cgs
Temperature21,500 K
Rotational velocity (v sin i)180 km/s
Details
E
Mass8.30[9] M☉
Radius3.77[9] R☉
Luminosity3,162[17] L☉
Surface gravity (log g)4.2±0.2[17] cgs
Temperature22,500[9] K
Rotation1.190847 days[9]
Rotational velocity (v sin i)140±10[17] km/s
Age0.4-0.9[17] Myr
Other designations
Sigma Orionis, Sigma Ori, σ Orionis, σ Ori, 48 Orionis, 48 Ori
AB: HD 37468, HR 1931, HIP 26549, SAO 132406, BD−02°1326, 2MASS J05384476-0236001, Mayrit AB
C: 2MASS J05384411-0236062, Mayrit 11238
D: HIP 26551, 2MASS J05384561-0235588, Mayrit 13084
E: V1030 Orionis, HR 1932, HD 37479, BD−02°1327, 2MASS J05384719-0235405, Mayrit 41062
Database references
SIMBADσ Ori
σ Ori C
σ Ori D
σ Ori E
σ Ori Cluster

Sigma Orionis or Sigma Ori (σ Orionis, σ Ori) is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates. The combined brightness of the component stars is magnitude 3.80.

  1. ^ a b Wu, Zhen-Yu; Zhou, Xu; Ma, Jun; Du, Cui-Hua (2009). "The orbits of open clusters in the Galaxy". Monthly Notices of the Royal Astronomical Society. 399 (4): 2146. arXiv:0909.3737. Bibcode:2009MNRAS.399.2146W. doi:10.1111/j.1365-2966.2009.15416.x. S2CID 6066790.
  2. ^ 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.
  3. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  4. ^ Caballero, J. A. (2014). "Stellar multiplicity in the sigma Orionis cluster: A review". The Observatory. 134: 273. arXiv:1408.2231. Bibcode:2014Obs...134..273C.
  5. ^ a b Echevarria, J.; Roth, M.; Warman, J. (1979). "Photometric Study of Trapezium-Type Systems". Revista Mexicana de Astronomía y Astrofísica. 4: 287. Bibcode:1979RMxAA...4..287E.
  6. ^ a b c Cite error: The named reference caballero2007 was invoked but never defined (see the help page).
  7. ^ a b Greenstein, Jesse L.; Wallerstein, George (1958). "The Helium-Rich Star, Sigma Orionis E". Astrophysical Journal. 127: 237. Bibcode:1958ApJ...127..237G. doi:10.1086/146456.
  8. ^ a b Guetter, H. H. (1979). "Photometric studies of stars in ORI OB1 /belt/". Astronomical Journal. 84: 1846. Bibcode:1979AJ.....84.1846G. doi:10.1086/112616.
  9. ^ a b c d e Cite error: The named reference townsend was invoked but never defined (see the help page).
  10. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  11. ^ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
  12. ^ a b 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.
  13. ^ a b c Schaefer, G. H.; Hummel, C. A.; Gies, D. R.; Zavala, R. T.; Monnier, J. D.; Walter, F. M.; Turner, N. H.; Baron, F.; ten Brummelaar, T. (2016-12-01). "Orbits, Distance, and Stellar Masses of the Massive Triple Star sigma Orionis". The Astronomical Journal. 152 (6): 213. arXiv:1610.01984. Bibcode:2016AJ....152..213S. doi:10.3847/0004-6256/152/6/213. ISSN 0004-6256. S2CID 36047128.
  14. ^ a b Simón-Díaz, S.; Caballero, J. A.; Lorenzo, J.; Maíz Apellániz, J.; Schneider, F. R. N.; Negueruela, I.; Barbá, R. H.; Dorda, R.; Marco, A.; Montes, D.; Pellerin, A.; Sanchez-Bermudez, J.; Sódor, Á.; Sota, A. (2015). "Orbital and Physical Properties of the σ Ori Aa, Ab, B Triple System". The Astrophysical Journal. 799 (2): 169. arXiv:1412.3469. Bibcode:2015ApJ...799..169S. doi:10.1088/0004-637X/799/2/169. S2CID 118500350.
  15. ^ Cite error: The named reference hummel was invoked but never defined (see the help page).
  16. ^ Hunger, K.; Heber, U.; Groote, D. (1989). "The distance of the helium-variable B star HD 37479". Astronomy and Astrophysics. 224: 57. Bibcode:1989A&A...224...57H.
  17. ^ a b c d Cite error: The named reference Song was invoked but never defined (see the help page).