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21 Arietis

From Wikipedia, the free encyclopedia
Binary star system in the constellation Aries
21 Arietis
Observation data
Epoch J2000      Equinox J2000
ConstellationAries
Right ascension02h 15m 42.77662s[1]
Declination+25° 02′ 34.9627″[1]
Apparent magnitude (V)5.57[2] (6.40/6.48)[3]
Characteristics
Spectral typeF6 V[4]
U−Bcolor index+0.00[5]
B−Vcolor 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]
Distance167 ± 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°
Periastronepoch (T)1986.192 ± 0.012
Argument of periastron (ω)
(secondary)
84.16 ± 0.16°
Details
21 Ari A
Mass1.338 ± 0.032[7] M
Surface gravity (log g)4.12[8] cgs
Temperature6,299[8] K
Metallicity[Fe/H]+0.02[8] dex
Rotational velocity (v sin i)12.6[9] km/s
Age2.2[2] Gyr
21 Ari B
Mass1.374 ± 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
SIMBADdata

21 Arietis (abbreviated21 Ari) is abinary star[3] system in the northernconstellation ofAries.21 Arietis is theFlamsteed designation. It has a combinedapparent 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 annualparallax shift of 19.58 mas,[1] is 167light-years (51parsecs). The pair orbit each other with aperiod of 23.70 years and aneccentricity 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 agiant planet may be causing radial velocity variations. The purported planet would have a mass of1.40 ± 0.36 MJ, an orbital period of 925 days and orbit the primary star.[7]

References

[edit]
  1. ^abcdefvan 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. ^abcdHolmberg, 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. ^abcdEggleton, 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. ^abc"* 21 Ari".SIMBAD.Centre de données astronomiques de Strasbourg. Retrieved2012-07-18.
  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. ^abcMuterspaugh, 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. ^abcBalachandran, 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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