21 Arietis

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21 Arietis
Observation data
Epoch J2000       Equinox J2000
Constellation Aries
Right ascension 02h 15m 42.77662s [1]
Declination +25° 02′ 34.9627″ [1]
Apparent magnitude  (V)5.57 [2] (6.40/6.48) [3]
Characteristics
Spectral type F6 V [4]
U−B color index +0.00 [5]
B−V color index +0.50 [5]
Astrometry
Radial velocity (Rv)−44.3 km/s
Proper motion (μ)RA: −89.72 [1] mas/yr
Dec.: −86.42 [1] mas/yr
Parallax (π)19.58±0.61  mas [1]
Distance 167 ± 5  ly
(51 ± 2  pc)
Absolute magnitude  (MV)2.03 [2]
Orbit [6]
Period (P)23.70 ± 0.12  yr
Semi-major axis (a)0.2353 ± 0.0011″
Eccentricity (e)0.6816 ± 0.0037
Inclination (i)104.52 ± 0.16°
Longitude of the node (Ω)236.44 ± 0.22°
Periastron epoch (T)1986.192 ± 0.012
Argument of periastron (ω)
(secondary)		84.16 ± 0.16°
Details
21 Ari A
Mass 1.338 ± 0.032 [7]   M☉
Surface gravity (log g)4.12 [8]   cgs
Temperature 6,299 [8]   K
Metallicity [Fe/H]+0.02 [8]   dex
Rotational velocity (v sin i)12.6 [9]  km/s
Age 2.2 [2]   Gyr
21 Ari B
Mass 1.374 ± 0.027 [7]   M☉
Other designations
BD+24 329, FK5 1059, HD 13872, HIP 10535, HR 657, SAO 75238, WDS J02157+2503. [5]
Database references
SIMBAD data

21 Arietis (abbreviated 21 Ari) is a binary star [3] system in the northern constellation of Aries. 21 Arietis is the Flamsteed designation. It has a combined apparent visual magnitude is 5.57; [2] the brighter member is magnitude 6.40 while the fainter star is magnitude 6.48. [3] The distance to this star system, based upon an annual parallax shift of 19.58  mas, [1] is 167 light-years (51 parsecs ). The pair orbit each other with a period of 23.70 years and an eccentricity of 0.68. [3]

The system was initially thought to be a triple system in 1981, since the orbit of the system predicted a mass greater than would be expected from its F6V spectral type. [10] This was later rejected because the distance to the system was overestimated. However, while observing the spectrum of the system, it was found that a giant planet may be causing radial velocity variations. The purported planet would have a mass of 1.40 ± 0.36 MJ, an orbital period of 925 days and orbit the primary star. [7]

References

  1. 1 2 3 4 5 6 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, S2CID   18759600.
  2. 1 2 3 4 Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv: 0811.3982 , Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID   118577511.
  3. 1 2 3 4 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 , S2CID   14878976.
  4. ↑ Harlan, E. A. (September 1969), "MK classifications for F- and G-type stars. I", Astronomical Journal, 74: 916–919, Bibcode:1969AJ.....74..916H, doi:10.1086/110881.
  5. 1 2 3 "* 21 Ari". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2012-07-18.
  6. ↑ Hartkopf, William I.; Mason, Brian D.; McAlister, Harold A. (January 1996), "Binary Star Orbits From Speckle Interferometry. VIII. Orbits of 37 Close Visual System", Astronomical Journal, 111: 370, Bibcode:1996AJ....111..370H, doi: 10.1086/117790 .
  7. 1 2 3 Muterspaugh, Matthew W.; Lane, Benjamin F.; Kulkarni, S. R.; Konacki, Maciej; Burke, Bernard F.; Colavita, M. M.; Shao, M.; Hartkopf, William I.; Boss, Alan P.; Williamson, M. (2010). "The Phases Differential Astrometry Data Archive. V. Candidate Substellar Companions to Binary Systems". The Astronomical Journal. 140 (6): 1657. arXiv: 1010.4048 . Bibcode:2010AJ....140.1657M. doi:10.1088/0004-6256/140/6/1657. S2CID   59585356.
  8. 1 2 3 Balachandran, Suchitra (May 1, 1990), "Lithium depletion and rotation in main-sequence stars", Astrophysical Journal, Part 1, 354: 310–332, Bibcode:1990ApJ...354..310B, doi:10.1086/168691.
  9. ↑ Schröder, C.; Reiners, Ansgar; Schmitt, Jürgen H. M. M. (January 2009), "Ca II HK emission in rapidly rotating stars. Evidence for an onset of the solar-type dynamo" (PDF), Astronomy and Astrophysics, 493 (3): 1099–1107, Bibcode:2009A&A...493.1099S, doi: 10.1051/0004-6361:200810377 [ permanent dead link ]
  10. ↑ Couteau, P.; Morel, P. J. (1982). "Is 21 Ari = Cou 79 a multiple system?". Astronomy and Astrophysics. 105: 323. Bibcode:1982A&A...105..323C.


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