74 Aquarii

74 Aquarii (abbreviated 74 Aqr) is a triple star[12] 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,[5] although it is very slightly variable,[3] and it is located at a distance of 590 light-years (180 parsecs) from Earth.

74 Aquarii

A light curve for HI Aquarii, plotted from TESS data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 53m 28.70492s[2]
Declination −11° 36′ 59.4532″[2]
Apparent magnitude (V) 5.8[3]
Characteristics
Spectral type B8IV/V[4] (B9pHgMn)[3])
U−B color index −0.245[5]
B−V color index −0.082[5]
Variable type a2 CVn[3]
Astrometry
Proper motion (μ) RA: +21.539[2] mas/yr
Dec.: +2.282[2] mas/yr
Parallax (π)5.5008 ± 0.6556 mas[2]
Distanceapprox. 590 ly
(approx. 180 pc)
Absolute magnitude (MV)−1.19[6]
Orbit[7]
Primary74 Aquarii A
Companion74 Aquarii B
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[8]
Primary74 Aquarii Aa
Companion74 Aquarii Ab
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
Aa
Mass2.72[9] M☉
Rotational velocity (v sin i)20[10] km/s
Ab
Mass2.53[9] M☉
B
Mass3.11[9] M☉
Other designations
HI Aqr, BD–12 6371, HD 216494, HIP 113031, HR 8704, SAO 165359[11]
Database references
SIMBADdata

Visual binary

74 Aquarii is a double star with the two components separated by about 0.1″.[13] The two components are referred to as A and B or AB and C in different publications.[7][8] The pair form a binary with a period of 9.5 years at a typical angular separation of 0.046″, but the orbit is highly eccentric.[7] 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.[12]

Spectroscopic binary

The primary star of the visual pair is a double-lined spectroscopic binary, where the presence of both components is revealed from the Doppler shift of their spectral lines, meaning 74 Aquarii is a triple system. The spectroscopic binary was discovered and the orbit calculated by Richard J. Wolff of the University of Hawaii in 1974.[14] A refined orbit was calculated in 2004 by Italian astronomers Giovanni Catanzaro and Paolo Leto in 2004. The orbital period is 3.4 days and the orbit is nearly circular.[8]

Components

The three stars have a combined spectral type of B8 or B9 and all three are thought to be similar. It is unclear whether the stars are on the main sequence, subgiants, or giant stars.[9][15][4] The two visual components are both chemically peculiar stars, the brighter of the two being a mercury-manganese star and the fainter an Ap/Bp star with an excess of mercury.[13] 74 Aquarii is an a2 CVn variable star, with a total amplitude of just 0.01 magnitudes,[3] and a period of 3.5892 days.[16]

References
  1. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
  2. 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. Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1: B/gcvs, Bibcode:2009yCat....102025S.
  4. 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.
  5. Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, Publicaciones Universidad de Chile, Department de Astronomy, 1: 1–17, Bibcode:1966PDAUC...1....1G.
  6. 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, S2CID 119257644.
  7. 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, S2CID 118429576.
  8. 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.
  9. Tokovinin, Andrei (2018-03-01), "The Updated Multiple Star Catalog", The Astrophysical Journal Supplement Series, 235 (1): 6, arXiv:1712.04750, Bibcode:2018ApJS..235....6T, doi:10.3847/1538-4365/aaa1a5, ISSN 0067-0049, S2CID 119047709.
  10. 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.
  11. "* 74 Aqr", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2012-07-01.
  12. 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, S2CID 119273467.
  13. Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
  14. Wolff, Richard J (1974), "Orbit of the Manganese Star HR 8704", Publications of the Astronomical Society of the Pacific, 86 (510): 173–175, Bibcode:1974PASP...86..173W, doi:10.1086/129576.
  15. Skiff, B. A. (2014), "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009- )", VizieR On-line Data Catalog, Bibcode:2014yCat....1.2023S.
  16. "HI Aqr". The International Variable Star Index. AAVSO. Retrieved 5 December 2022.
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