Astronomy:Iota Aquarii

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Short description: B-type main sequence star in the constellation Aquarius
Iota Aquarii
Location of ι Aquarii (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Aquarius[1]
Right ascension  22h 06m 26.227s[2]
Declination −13° 52′ 10.85″[2]
Apparent magnitude (V) 4.279[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type B8 V[5]
U−B color index −0.288[3]
B−V color index −0.062[3]
Variable type constant[6]
Astrometry
Radial velocity (Rv)−10.0[7] km/s
Proper motion (μ) RA: +42.210[2] mas/yr
Dec.: −56.566[2] mas/yr
Parallax (π)18.62 ± 0.22[8] mas
Distance175 ± 2 ly
(53.7 ± 0.6 pc)
Absolute magnitude (MV)+0.64[1]
Details
A
Mass2.9[9] M☉
Radius2.1[9] R☉
Luminosity74[1] L☉
Surface gravity (log g)4.09±0.08[10] cgs
Temperature11,700[9] K
Metallicity [Fe/H]−0.08±0.12[10] dex
Rotational velocity (v sin i)135[11] km/s
Age70[9] Myr
B
Mass1.2[9] M☉
Radius1.1[9] R☉
Temperature6,350[9] K
Rotational velocity (v sin i)20[12] km/s
Other designations
ι Aquarii, ι Aqr, 33 Aquarii, BD−14 6209, FK5 828, GC 30914, HD 209819, HIP 109139, HR 8418, SAO 164861, PPM 239801[13]
Database references
SIMBADdata

Iota Aquarii is a binary star[12][9] system in the equatorial constellation of Aquarius. Its identifier is a Bayer designation that is Latinised from ι Aquarii, and abbreviated Iota Aqr or ι Aqr. This star is visible to the naked eye with an apparent magnitude of +4.279.[3] Based upon parallax measurements, the distance to this star is around 175 light-years (54 parsecs).[2] The system is drifting closer to the Sun with a radial velocity of −10 km/s.[7]

Iota Aquarii was first catalogued in Uranometria in 1603; the binary nature of this system was discovered in 2009 following a radial velocity survey using the HARPS instrument.[6] A 2010 infrared search for companions around this star was unsuccessful.[14] The presence of a stellar companion was confirmed through direct spectral detection in 2016. The companion shows a significant velocity variation over a 77-day interval, suggesting a short orbital period.[12] The companion was re-observed in 2024, showing a projected separation of 0.38 astronomical units. Together with the masses of the components, this suggests an orbital period of roughly 40 days.[9]

The spectrum of the primary, component A, fits a stellar classification of B8 V,[5] suggesting that this is a B-type main-sequence star. It is roughly 70 million years old[9] and is spinning rapidly with a projected rotational velocity of 135 km/s.[11] The star has 2.9 times the mass of the Sun and 2.1 times the Sun's radius.[9] It is radiating 74[1] times the luminosity of the Sun from its photosphere at an effective temperature of 11,700 K.[9] The secondary, component B, has 1.2 times the mass of the Sun, 1.1 times the radius, and an effective temperature of 6,350 K.[9] The system is a source for X-ray emission.[15]

There is evidence for a third companion based on the difference of proper motion measurements by the Hipparcos and Gaia spacecrafts. Such a companion would have an orbital period of roughly one year, and be either a faint red dwarf or a white dwarf.[9]

References

  1. ↑ 1.0 1.1 1.2 1.3 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series 61: 387–405, Bibcode: 1985A&AS...61..387K. 
  4. ↑ Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy and Astrophysics 537: A120. doi:10.1051/0004-6361/201117691. Bibcode: 2012A&A...537A.120Z. 
  5. ↑ 5.0 5.1 Houk, Nancy (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. 
  6. ↑ 6.0 6.1 Lagrange, A. -M. et al. (2009), "Extrasolar planets and brown dwarfs around A-F type stars. VI. High precision RV survey of early type dwarfs with HARPS", Astronomy & Astrophysics 495 (1): 335–352, doi:10.1051/0004-6361:200810105, Bibcode: 2009A&A...495..335L. 
  7. ↑ 7.0 7.1 Wielen, R. et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg (Astronomisches Rechen-Institut Heidelberg) 35 (35): 1, Bibcode: 1999VeARI..35....1W. 
  8. ↑ van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V .
  9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 9.12 9.13 Waisberg, Idel; Klein, Ygal; Katz, Boaz (2026-02-19), "Hidden Companions to Intermediate-mass Stars. XXXV. Unveiling a 1.2 M☉, 0.38 au Companion to Iota Aquarii", Research Notes of the AAS 10 (2): 34, doi:10.3847/2515-5172/ae468c, ISSN 2515-5172 .
  10. ↑ 10.0 10.1 Wu, Yue et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics 525: A71, doi:10.1051/0004-6361/201015014, Bibcode: 2011A&A...525A..71W. 
  11. ↑ 11.0 11.1 Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal 573 (1): 359–365, doi:10.1086/340590, Bibcode: 2002ApJ...573..359A. 
  12. ↑ 12.0 12.1 12.2 Gullikson, Kevin et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal 152 (2): 13, doi:10.3847/0004-6256/152/2/40, 40, Bibcode: 2016AJ....152...40G. 
    Note: the observations were made on modified Julian dates 6447.91 and 6524.67, which are separated by 76.76 days.
  13. ↑ "* iot Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+iot+Aqr. 
  14. ↑ Ehrenreich, D. et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics 523: A73, doi:10.1051/0004-6361/201014763, Bibcode: 2010A&A...523A..73E. 
  15. ↑ Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement 184 (1): 138–151, doi:10.1088/0067-0049/184/1/138, Bibcode: 2009ApJS..184..138H. 



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