Iota Orionis

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ι Orionis
Location of ι Ori (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 35m 25.98191s[1]
Declination –05° 54′ 35.6435″[1]
Apparent magnitude (V) 2.77[2]
Characteristics
ι Orionis A
Spectral type O9 III + B0.8 III/IV[3] + B2:IV:[4]
U−B color index –1.08[2]
B−V color index –0.24[2]
ι Orionis B
Spectral type B8 III[5]
Variable type Orion[6]
Distance
412+14
−13[4] pc
Periastron epoch
(T)		2,450,072.80 HJD
Details
ι Ori Aa1
Myr
ι Ori B
Myr
V2451 Ori, 2MASS J05352645-0554445
ι Ori C: 2MASS J05352920-0554471
Database references
SIMBADι Ori
ι Ori B
ι Ori C

Iota Orionis (ι Orionis, abbreviated ι Ori) is a multiple star system in the equatorial constellation of Orion the hunter. It is the eighth-brightest member of Orion with an apparent visual magnitude of 2.77 and also the brightest member of the asterism known as Orion's Sword. It is a member of the NGC 1980 open cluster. From parallax measurements, it is located at a distance of roughly 1,340 light-years (412 parsecs) from the Sun.

The system has three visible components designated Iota Orionis A, B and C. Iota Orionis A has also been resolved using speckle interferometry and is also a massive spectroscopic binary, with components Iota Orionis Aa1 (officially named Hatysa /hɑːˈtiːsə/), Aa2, and Ab.

Nomenclature

ι Orionis (Latinised to Iota Orionis) is the system's Bayer designation. The designations of the three constituents as Iota Orionis A, B and C, and those of A's components - Iota Orionis Aa1, Aa2, and Ab - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[12]

The system has the traditional name Nair al Saif, from the Arabic نير السيف nayyir as-sayf "the Bright One of the Sword", though this is little used.[13][14][15] Since Antonín Bečvář's 1951 Atlas Coeli, it has borne the proper name Hatysa. Kunitzsch was unable to find an older source for the latter name.[16]

In 2016, the IAU organized a

multiple systems.[18] It approved the name Hatysa for the component Iota Orionis Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[19]

Iota Orionis B is a variable star and in 2011 it was given the

variable star designation V2451 Orionis.[6]

Distance

ι Orionis is the bright star to the right (south) of the Orion Nebula

Iota Orionis has a parallax of 1.40±0.22 

Gaia Data Release 2 has individual parallaxes for the two fainter components of the Iota Orionis star system of 2.3839±0.0810 mas and 2.5321±0.0484 mas,[21][22] indicating distances of 419 pc and 395 pc respectively, with margins of error of just a few parsecs. There is little doubt that all three stars are at the same distance.[3][8]

Iota Orionis is generally assumed to be associated with the open cluster NGC 1980, which is at a distance of around 400 pc. However, they may not lie at exactly the same distance and Iota Orionis may have a complex history involving stellar encounters and runaway stars.

1887.[24]

Properties

Iota Orionis is dominated by the multiple star Iota Orionis A. It is clearly identified as a double-lined spectroscopic binary whose components are a

speckle interferometry and is probably a B2 subgiant.[4][11]

The primary component of Iota Orionis A is a class O

spectroscopic binary pair is a class B giant or subgiant
with a mass of about 13 M☉. It has a temperature of 27,000 K and radius of 5.4 R☉, resulting in it radiating over 8,000 times as much energy as the sun.

Iota Orionis B is a B8 giant at 11" (approximately 5,000 AU

helium-weak chemically peculiar star.[27] The fainter Iota Orionis C is an A0 star at 49".[28]

References

  1. ^
    S2CID 18759600
    .
  2. ^
    Bibcode:1978A&AS...34....1N
    .
  3. ^
    doi:10.1086/321367
    .
  4. ^
    S2CID 211532687
    .
  5. ^
    doi:10.1086/525529
    .
  6. ^
    Bibcode:2011IBVS.5969....1K
    .
  7. Bibcode:1967IAUS...30...57E
    .
  8. ^
    doi:10.1046/j.1365-8711.2000.03542.x
    .
  9. ^
    Bibcode:1970A&A.....8..197C
    .
  10. Bibcode:1970crvs.book.....U
    .
  11. ^ a b "Multiple Star Catalog". Archived from the original on 2021-01-22. Retrieved 2021-01-17.
  12. arXiv:1012.0707 [astro-ph.SR
    ].
  13. ^ Allen, Richard Hinckley (1899). Star-names and their meanings. G. E. Stechert. p. 317.
  14. ^ Hoffleit, D. "Bright Star Catalogue, 5th Revised Ed. (note)". VizieR. Centre de Données astronomiques de Strasbourg. Retrieved 28 October 2018.
  15. ISBN 0-521-44921-9
    .
  16. ISBN 1-931559-44-9
    .
  17. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  18. ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  19. ^ "Naming Stars". IAU.org. Retrieved 16 December 2017.
  20. Bibcode:1997A&A...323L..49P
    .
  21. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR
    .
  22. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR
    .
  23. S2CID 119428410
    .
  24. doi:10.1002/asna.200410256
    .
  25. Bibcode:1978rmsa.book.....M
    .
  26. doi:10.1051/0004-6361:20000014
    .
  27. doi:10.1051/0004-6361/200810788
    .
  28. Bibcode:1954TrSht..25....1P
    .

External links
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