Epoch J2000 Equinox J2000
|Right ascension||02h 59m 12.72536s|
|Declination||+21° 20′ 25.5575″|
|Apparent magnitude (V)||4.63 (5.2/5.5)|
|Spectral type||A2 Vs + A2 Vs|
|U−B color index||+0.08|
|B−V color index||+0.04|
|R−I color index||0.02|
|Radial velocity (Rv)||+0.9 ± 0.9 km/s|
|Proper motion (μ)||RA: -13.74 mas/yr
Dec.: -5.12 mas/yr
|Parallax (π)||9.81 ± 0.79 mas|
|Distance||330 ± 30 ly
(102 ± 8 pc)
|ε Ari A|
|Rotational velocity (v sin i)||60 km/s|
|ε Ari B|
|Rotational velocity (v sin i)||60 km/s|
|ε Ari A: HD 18520, HR 888, SAO 75673.|
|ε Ari B: HD 18519, HR 887.|
Epsilon Arietis (ε Ari, ε Arietis) is the Bayer designation for a visual binary star system in the northern constellation of Aries. It has a combined apparent visual magnitude of 4.63 and can be seen with the naked eye, although the two components are too close together to be resolved without a telescope. With an annual parallax shift of 9.81 mas, the distance to this system can be estimated as 330 light-years (100 parsecs), give or take a 30 light-year margin of error.
The brighter member of this pair has an apparent magnitude of 5.2. At an angular separation of 1.426 ± 0.010 arcseconds from the brighter component, along a position angle of 209.2° ± 0.3°, is the magnitude 5.5 companion. Both are A-type main sequence stars with a stellar classification of A2 Vs. (The 's' suffix indicates that the absorption lines in the spectrum are distinctly narrow.) In the 2009 Catalogue of Ap, HgMn and Am stars, the two stars have a classification of A3 Ti, indicating they are Ap stars with an anomalous abundance of titanium. Within the measurement margin of error, their projected rotational velocities are deemed identical at 60 km/s.
This star system, along with δ Ari, ζ Ari, π Ari, and ρ3 Ari, were Al Bīrūnī's Al Buṭain (ألبطين), the dual of Al Baṭn, the Belly. According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Buṭain were the title for five stars :δ Ari as Botein, π Ari as Al Buṭain I, ρ3 Ari as Al Buṭain II, ε Ari as Al Buṭain III dan ζ Ari as Al Buṭain IV
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv: , Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
- Eggen, Olin J. (November 1963), "Luminosities, colors, and motions of the brightest A-type stars", Astronomical Journal, 68: 697, Bibcode:1963AJ.....68..697E, doi:10.1086/109198.
- Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi:10.1051/0004-6361/200810788.
- Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics, 393: 897–911, arXiv: , Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943.
- Gontcharov, G. A. (November 2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065.
- "CCDM J02592+2120AB -- Double or multiple star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2012-08-05.
- Scardia, M.; Prieur, J.-L.; Pansecchi, L.; Argyle, R. W.; Basso, S.; Sala, M.; Ghigo, M.; Koechlin, L.; Aristidi, E. (January 2007), "Speckle observations with PISCO in Merate - III. Astrometric measurements of visual binaries in 2005 and scale calibration with a grating mask", Monthly Notices of the Royal Astronomical Society, 374 (3): 965–978, Bibcode:2007MNRAS.374..965S, doi:10.1111/j.1365-2966.2006.11206.x.
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 83. ISBN 0-486-21079-0. Retrieved 2010-12-12.
- Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971