Iota Gruis

Iota Gruis, Latinized from ι Gruis, is a binary star[6] system in the southern constellation of Grus. It has an apparent visual magnitude of 3.90,[2] which is bright enough to be seen with the naked eye at night. The distance to this system, as determined using an annual parallax shift of 17.80 mas as seen from the Earth,[1] is about 183 light years.

Iota Gruis
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Grus
Right ascension 23h 10m 21.53755s[1]
Declination −45° 14′ 48.1647″[1]
Apparent magnitude (V) 3.90[2]
Characteristics
Spectral type K1 III[3]
U−B color index +0.86[2]
B−V color index +1.02[2]
Astrometry
Radial velocity (Rv)−4.4[4] km/s
Proper motion (μ) RA: +132.50[1] mas/yr
Dec.: −26.66[1] mas/yr
Parallax (π)17.80 ± 0.33 mas[1]
Distance183 ± 3 ly
(56 ± 1 pc)
Absolute magnitude (MV)+0.13[5]
Orbit[6][7]
Period (P)409.614 d
Semi-major axis (a)7.82±0.47 mas
Eccentricity (e)0.66
Inclination (i)114.3±5.2°
Periastron epoch (T)2416115.569 JD
Argument of periastron (ω)
(secondary)		240.8°
Semi-amplitude (K1)
(primary)		13.6 km/s
Details
ι Gru A
Luminosity107[5] L☉
Other designations
ι Gru, CD−45° 14947, FK5 1605, HD 218670, HIP 114421, HR 8820, SAO 231468[8]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 409.6 days (1.121 years) and an eccentricity of 0.66.[6] The yellow-hued primary component is an evolved K-type giant star with a stellar classification of K1 III.[3] It is an X-ray emitter with a flux of 441.31×10−17 W/m2.[9]

References
  1. 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.
  2. 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.
  3. Houk, N. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 2, Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H.
  4. Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Carnegie Institute of Washington D.C., Bibcode:1953GCRV..C......0W.
  5. 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.
  6. Pourbaix, D.; et al. (2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424 (2): 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  7. Jancart, S.; et al. (2005), "Astrometric orbits of SB9 stars", Astronomy and Astrophysics, 442 (1): 365–380, arXiv:astro-ph/0507695, Bibcode:2005A&A...442..365J, doi:10.1051/0004-6361:20053003, S2CID 15123997.
  8. "iot Gru". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-26.
  9. Hunsch, M.; et al. (January 1998), "The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants", Astronomy and Astrophysics Supplement, 127 (2): 251–255, Bibcode:1998A&AS..127..251H, doi:10.1051/aas:1998347.
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