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 | |
| 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
[edit]- ^ a b c d e f 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.
- ^ a b c d 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.
- ^ a b c d 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.
- ^ 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.
- ^ a b c "* 21 Ari". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-18.
- ^ 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.
- ^ a b c 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.
- ^ a b c 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.
- ^ 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]
- ^ Couteau, P.; Morel, P. J. (1982). "Is 21 Ari = Cou 79 a multiple system?". Astronomy and Astrophysics. 105: 323. Bibcode:1982A&A...105..323C.
External links
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