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Binary star system in the constellation Aries From Wikipedia, the free encyclopedia
Epsilon Arietis (ε Ari, ε Arietis) is the Bayer designation for a visual binary[8] 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. It is located behind the dark cloud MBM12.[6]
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 mas[1] |
Distance | 330 ± 30 ly (102 ± 8 pc) |
Orbit[6] | |
Period (P) | 704.111±1.778 yr |
Semi-major axis (a) | 2.174±0.035″ |
Eccentricity (e) | 0.317±0.006 |
Inclination (i) | 84.2±0.8° |
Longitude of the node (Ω) | 25.6±0.7° |
Periastron epoch (T) | 704.111±1.778 |
Argument of periastron (ω) (secondary) | 162.1±1.0° |
Details | |
ε Ari A | |
Mass | 2.4[6] M☉ |
Rotational velocity (v sin i) | 60[4] km/s |
ε Ari B | |
Mass | 2.4[6] M☉ |
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. | |
Database references | |
SIMBAD | ε Ari |
ε Ari A | |
ε Ari B |
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°,[8] 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]
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.[9] 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 and ζ Ari as Al Buṭain IV[10]
In Chinese astronomy, Epsilon Arietis may be or may be part of Tso Kang (from Cantonese 左更 zogang, Mandarin pronunciation zuǒgēng).[11][12]
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