Iota Apodis

Iota Apodis (ι Aps, ι Apodis) is the Bayer designation for a binary star[3] system in the southern circumpolar constellation of Apus. It is a faint target at an apparent visual magnitude of 5.41,[2] but still visible to the naked eye from suitably dark skies. The distance to this star can be roughly gauged from parallax measurements, yielding an estimate of 1,300 light-years (400 parsecs) with a 20% margin of error.[1]

Iota Apodis
Location of ι Apodis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Apus
Right ascension 17h 22m 05.87559s[1]
Declination –70° 07′ 23.5400″[1]
Apparent magnitude (V) 5.41[2] (5.90/6.46)[3]
Characteristics
Spectral type B9 V + B9.5 V[3]
U−B color index −0.23[2]
B−V color index −0.04[2]
Astrometry
Radial velocity (Rv)−4.3[4] km/s
Proper motion (μ) RA: −1.844 ± 0.266[5] mas/yr
Dec.: −10.811 ± 0.303[5] mas/yr
Parallax (π)3.1403 ± 0.1782 mas[5]
Distance1,040 ± 60 ly
(320 ± 20 pc)
Orbit[6]
Period (P)59.32±3.0 yr
Semi-major axis (a)0.115±0.005″
Eccentricity (e)0.172±0.050
Inclination (i)69.4±3.0°
Longitude of the node (Ω)119.6±4.0°
Argument of periastron (ω)
(secondary)		270.5±7.0°
Details
ι Aps A
Mass3.89±1.02[6] M☉
ι Aps B
Mass3.45±0.90[6] M☉
Other designations
CPD−69 2719, FK5 642, HD 156190, HIP 84979, HR 6411, SAO 257491, WDS J17221−7007[7]
Database references
SIMBADdata

Both stars are B-type main sequence stars, which indicates they shine with a blue-white hue.[8] The brighter component has a stellar classification of B9 V and an apparent magnitude 5.90, while the second member is a B9.5 V star with a magnitude of 6.46. The pair have an angular separation of 0.091 arcseconds[3] with an estimated orbital period of 59.32 years. They are about 3.89 and 3.45 times as massive as the Sun.[6]

Naming

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of ι Apodis, ζ Apodis, β Apodis, γ Apodis, δ Octantis, δ1 Apodis, η Apodis, α Apodis and ε Apodis. Consequently, ι Apodis itself is known as 異雀二 (Yì Què èr, English: the Second Star of Exotic Bird.)[9]

References
  1. van Leeuwen, F. (November 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. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. 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.
  4. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W.
  5. 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.
  6. Docobo, J. A.; Andrade, M. (January 2013), "Dynamical and physical properties of 22 binaries discovered by W. S. Finsen", Monthly Notices of the Royal Astronomical Society, 428 (1): 321–339, Bibcode:2013MNRAS.428..321D, doi:10.1093/mnras/sts045.
  7. "* iot Aps". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-09.{{cite web}}: CS1 maint: postscript (link)
  8. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16
  9. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日
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