74 Aquarii

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74 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 53m 28.70347s[1]
Declination –11° 36′ 59.4532″[1]
Apparent magnitude (V) 5.791[2]
Spectral type B8IV/V[3]
U−B color index –0.245[2]
B−V color index –0.082[2]
Variable type a2 CVn[4]
Proper motion (μ) RA: +20.81[1] mas/yr
Dec.: +1.69[1] mas/yr
Parallax (π) 4.96 ± 0.84[1] mas
Distance approx. 700 ly
(approx. 200 pc)
Rotational velocity (v sin i) 20[5] km/s
Other designations
BD–12 6371, HD 216494, HIP 113031, HR 8704, SAO 165359.[4]

74 Aquarii (abbreviated 74 Aqr) is a triple star[6] system in the constellation of Aquarius. 74 Aquarii is its Flamsteed designation and it also bears the variable star designation HI Aquarii. The combined apparent visual magnitude is 5.8[2] and it is located at a distance of 700 light-years (210 parsecs) from Earth.[1]

The inner pair of stars form a double-lined spectroscopic binary, where the presence of both components is revealed from the Doppler shift of their spectral lines. They have an orbital period of 3.4298 days. A third component is orbiting the inner pair with an 18 year period at a typical angular separation of 0.078 arcseconds. In 2010, this component was at an angular separation of 0.069 arcseconds along a position angle of 285.9°. This is equivalent to a projected separation of 13.9 ± 2.4 AU.[6]


  1. ^ a b c d e f van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752free to read, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357. 
  2. ^ a b c d Gutierrez-Moreno, Adelina; et al. (1966), A System of photometric standards, 1, Publicaciones Universidad de Chile, Department de Astronomy, pp. 1–17, Bibcode:1966PDAUC...1....1G. 
  3. ^ 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. 
  4. ^ a b "HI Aqr -- Variable Star of alpha2 CVn type", SIMBAD Astronomical Object Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-01. 
  5. ^ 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. 
  6. ^ a b Schöller, M.; et al. (November 2010), "Multiplicity of late-type B stars with HgMn peculiarity", Astronomy and Astrophysics, 522: A85, arXiv:1010.3643free to read, Bibcode:2010A&A...522A..85S, doi:10.1051/0004-6361/201014246. 

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