74 Aquarii

74 Aquarii (abbreviated 74 Aqr) is a triple star[8] 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]

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]
Characteristics
Spectral type B8IV/V[3]
U−B color index –0.245[2]
B−V color index –0.082[2]
Variable type a2 CVn[4]
Astrometry
Proper motion (μ) RA: +20.81[1] mas/yr
Dec.: +1.69[1] mas/yr
Parallax (π)4.96 ± 0.84[1] mas
Distanceapprox. 700 ly
(approx. 200 pc)
Orbit[5]
Primary74 Aquarii AB
Companion74 Aquarii C
Period (P)9.479±0.044 yr
Semi-major axis (a)0.0460±0.0061″
Eccentricity (e)0.862±0.029
Inclination (i)29.8±17.4°
Longitude of the node (Ω)40.9±20.3°
Periastron epoch (T)2010.039±0.134
Argument of periastron (ω)
(secondary)		70.7±16.1°
Orbit[6]
Primary74 Aquarii A
Companion74 Aquarii B
Period (P)3.429616±0.000004 d
Eccentricity (e)0.05±0.02
Periastron epoch (T)2452909.150±0.007 JD
Argument of periastron (ω)
(secondary)		86.5±0.8°
Semi-amplitude (K1)
(primary)		95±2 km/s
Semi-amplitude (K2)
(secondary)		113±2 km/s
Details
Rotational velocity (v sin i)20[7] km/s
Other designations
BD–12 6371, HD 216494, HIP 113031, HR 8704, SAO 165359.[4]
Database references
SIMBADdata

Spectroscopic binary

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. The spectroscopic binary was discovered and the orbit calculated by Richard J. Wolff of the University of Hawaii in 1974.[9] A refined orbit was calculated in 2004 by Italian astronomers Giovanni Catanzaro and Paolo Leto in 2004. The orbital period is 3.4 days.[6]

Visual binary

A third component is orbiting the inner pair with a 9.5-year period at a typical angular separation of 0.046 arcseconds.[5] 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.[8]

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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.
  2. 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. "* 74 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-01.
  5. Tokovinin, Andrei (2017). "New Orbits Based on Speckle Interferometry at SOAR. II". The Astronomical Journal. 154 (3). 110. arXiv:1708.01300. Bibcode:2017AJ....154..110T. doi:10.3847/1538-3881/aa8459.
  6. Catanzaro, G.; Leto, P. (2004). "Orbital solutions for SB2 systems with a HgMn component". Astronomy and Astrophysics. 416 (2): 661–668. Bibcode:2004A&A...416..661C. doi:10.1051/0004-6361:20034445.
  7. 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.
  8. Schöller, M.; et al. (November 2010), "Multiplicity of late-type B stars with HgMn peculiarity", Astronomy and Astrophysics, 522: A85, arXiv:1010.3643, Bibcode:2010A&A...522A..85S, doi:10.1051/0004-6361/201014246.
  9. Wolff, Richard J (1974). "Orbit of the Manganese Star HR 8704". Publications of the Astronomical Society of the Pacific. 86: 173–175. Bibcode:1974PASP...86..173W. doi:10.1086/129576.
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