51 Aquarii

51 Aquarii is a binary star[2] system located around 410[1] light years away from the Sun in the equatorial constellation of Aquarius. 51 Aquarii is its Flamsteed designation. It is visible to the naked eye as a dim, yellow-white hued star with a combined apparent visual magnitude of 5.78.[4] The system is moving further from the Earth with a heliocentric radial velocity of +6 km/s.[5]

51 Aquarii
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension  22h 24m 06.88433s[1]
Declination –04° 50′ 13.2692″[1]
Apparent magnitude (V) 5.78 (6.45 + 6.63)[2]
Characteristics
Spectral type A0 V[3] + A0[2]
U−B color index –0.11[4]
B−V color index –0.04[4]
Astrometry
Radial velocity (Rv)+6[5] km/s
Proper motion (μ) RA: +26.90[1] mas/yr
Dec.: –7.35[1] mas/yr
Parallax (π)8.04 ± 0.63[1] mas
Distance410 ± 30 ly
(124 ± 10 pc)
Orbit[6]
Period (P)145.07±1.85 yr
Semi-major axis (a)0.402±0.003″
Eccentricity (e)0.702±0.003
Inclination (i)161.4±0.7°
Longitude of the node (Ω)113.5±3.0°
Periastron epoch (T)1987.66±0.05
Argument of periastron (ω)
(secondary)		296.9±3.0°
Details
51 Aqr A
Mass2.80±0.10[7] M☉
Luminosity88.2+14.8
−14.2[7] L☉
Temperature10,328±71[7] K
Rotational velocity (v sin i)91[7] km/s
Other designations
51 Aqr, BD−05°5780, HD 212404, HIP 110578, HR 8533, SAO 146067, WDS J22241-0450[8]
Database references
SIMBADdata

The dual nature of this system was discovered by S. W. Burnham in 1873 with a 6 inches (15 cm) Alvan Clark refractor.[9] The pair orbit each other with a period of 145 years and a large eccentricity of 0.7.[6] The magnitude 6.45[2] primary, designated component A, is an A-type main sequence star with a stellar classification of A0 V.[3] It has a high rate of rotation with a projected rotational velocity of 91 km/s.[10] The secondary component has a matching class of A0 with a visual magnitude of 6.63.[2]

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. 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.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. 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.
  5. Wilson, R. E. (1953), General Catalogue of Stellar Radial Velocities, Carnegie Institute of Washington, D.C., Bibcode:1953GCRV..C......0W.
  6. Tokovinin, Andrei; Mason, Brian D.; Hartkopf, William I.; Mendez, Rene A.; Horch, Elliott P. (2015), "Speckle Interferometry at Soar in 2014", The Astronomical Journal, 150 (2): 50, arXiv:1506.05718, Bibcode:2015AJ....150...50T, doi:10.1088/0004-6256/150/2/50.
  7. Zorec, J.; Royer, F.; Asplund, Martin; Cassisi, Santi; Ramirez, Ivan; Melendez, Jorge; Bensby, Thomas; Feltzing, Sofia (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.
  8. "* 51 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-16.
  9. Docobo, J. A.; Ling, J. F. (April 2007), "Orbits and System Masses of 14 Visual Double Stars with Early-Type Components", The Astronomical Journal, 133 (4): 1209–1216, Bibcode:2007AJ....133.1209D, doi:10.1086/511070
  10. 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.
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