97 Aquarii

97 Aquarii (abbreviated 97 Aqr) is a binary star system in the equatorial constellation of Aquarius. 97 Aquarii is the Flamsteed designation. The combined apparent visual magnitude of the system is 5.20;[2] the brighter star is magnitude 5.59 while the companion is magnitude 6.72.[3] Based upon an annual parallax shift of 15.30 milliarcseconds,[1] this system is at a distance of around 210 light-years (64 parsecs) from Earth.

97 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  23h 22m 39.17113s[1]
Declination –15° 02′ 21.6245″[1]
Apparent magnitude (V) 5.20[2] (5.59/6.72)[3]
Characteristics
Spectral type A2 V + A7 V[4]
U−B color index +0.10[2]
B−V color index +0.20[2]
Astrometry
Radial velocity (Rv)–12[5] km/s
Proper motion (μ) RA: +117.00[1] mas/yr
Dec.: +16.48[1] mas/yr
Parallax (π)15.30 ± 0.79[1] mas
Distance210 ± 10 ly
(65 ± 3 pc)
Orbit[6]
Period (P)64.62 yr
Semi-major axis (a)0.408″
Eccentricity (e)0.140
Inclination (i)77.6°
Longitude of the node (Ω)276.3°
Periastron epoch (T)1941.29
Argument of periastron (ω)
(secondary)		354.6°
Details
Rotational velocity (v sin i)175[7] km/s
Other designations
BD–15° 6406, HD 220278, HIP 115404, HR 8890, SAO 165658.[8]
Database references
SIMBADdata

The two stars in this system orbit each other over a period of 64.62 years at an eccentricity of 0.14.[3] Both are A-type main sequence stars; the primary has a stellar classification of A2 V while its companion is A7 V.[4] Their composite spectrum shows the properties of a Lambda Boötis star, which means it displays peculiar abundances of certain elements.[9]

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. Nicolet, B. (1978), "Photoelectric photometric Catalogue of homogeneous measurements in the UBV System", Astronomy and Astrophysics Supplement Series, 34: 1–49, Bibcode:1978A&AS...34....1N.
  3. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x.
  4. Christy, James W.; Walker, R. L., Jr. (October 1969), "MK Classification of 142 Visual Binaries", Publications of the Astronomical Society of the Pacific, 81 (482): 643, Bibcode:1969PASP...81..643C, doi:10.1086/128831
  5. Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
  6. "New orbits", International Astronomical Union Commission 26 (Double Stars) (Information Circular No. 139): 1–2, 1999, Bibcode:1999IAUDS.139....1.
  7. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224.
  8. "* 97 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-17.
  9. Gerbaldi, M.; Faraggiana, R.; Lai, O. (December 2003), "The heterogeneous class of lambda Bootis stars", Astronomy and Astrophysics, 412: 447–464, Bibcode:2003A&A...412..447G, doi:10.1051/0004-6361:20031472.
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