Epsilon Arietis
 Location of ε Arietis (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Aries |
| Right ascension | 02h 59m 12.72536s[1] |
| Declination | +21° 20′ 25.5575″[1] |
| Apparent magnitude (V) | 4.63[2] (5.2/5.5)[3] |
| Characteristics | |
| Spectral type | A2 Vs + A2 Vs[4] |
| U−B color index | +0.08[2] |
| B−V color index | +0.04[2] |
| R−I color index | 0.02 |
| Astrometry | |
| Radial velocity (Rv) | +0.9 ± 0.9[5] km/s |
| Proper motion (μ) | RA: -13.74[1] mas/yr Dec.: -5.12[1] mas/yr |
| Parallax (π) | 9.81 ± 0.79[1] mas |
| Distance | 330 ± 30 ly (102 ± 8 pc) |
| Details | |
| ε Ari A | |
| Rotational velocity (v sin i) | 60[4] km/s |
| ε Ari B | |
| Rotational velocity (v sin i) | 60[4] km/s |
| Other designations | |
| 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[7] star system in the northern constellation of Aries. It has a combined apparent visual magnitude of 4.63[2] 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,[1] 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.[3] At an angular separation of 1.426 ± 0.010 arcseconds from the brighter component, along a position angle of 209.2° ± 0.3°,[7] is the magnitude 5.5 companion.[3] Both are A-type main sequence stars with a stellar classification of A2 Vs.[4] (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,[3] 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.[4]
Name
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.[8] 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[9]
References
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- ↑ 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
