Iota Aquarii

Iota Aquarii
Location of ι Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
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 mas/yr[2]
Dec.: −56.566 mas/yr[2]
Parallax (π)18.62±0.22 mas[8]
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
Metallicity [Fe/H]−0.5[12] dex
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. ^ a b c d 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. XHIP record for this object at VizieR.
  2. ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c d 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. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  5. ^ a b Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  6. ^ a b 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, arXiv:0809.4636, Bibcode:2009A&A...495..335L, doi:10.1051/0004-6361:200810105, S2CID 62894956.
  7. ^ a b 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, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
  8. ^ 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.
  9. ^ a b c d e f g h i j k l m n 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{{citation}}: CS1 maint: unflagged free DOI (link).
  10. ^ a b Wu, Yue; et al. (January 2011), "Coudé-feed stellar spectral library - atmospheric parameters", Astronomy and Astrophysics, 525: A71, arXiv:1009.1491, Bibcode:2011A&A...525A..71W, doi:10.1051/0004-6361/201015014, S2CID 53480665.
  11. ^ a b Abt, Helmut A.; Levato, Hugo; Grosso, Monica (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
  12. ^ a b c d Gullikson, Kevin; et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 13, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065, 40.
    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. Retrieved 2012-06-30.
  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, arXiv:1007.0002, Bibcode:2010A&A...523A..73E, doi:10.1051/0004-6361/201014763, S2CID 54913363.
  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, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138, S2CID 119267456.
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