Epsilon Arietis

ε 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 mas[1]
Distance330 ± 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
Mass2.4[6] M☉
Rotational velocity (v sin i)60[4] km/s
ε Ari B
Mass2.4[6] M☉
Rotational velocity (v sin i)60[4] km/s
Other designations
48 Arietis, BD+20 484, HIP 13914, ADS 2257, WDS J02592+2120AB[7]
ε Ari A: HD 18520, HR 888, SAO 75673
ε Ari B: HD 18519, HR 887.
Database references
SIMBADε Ari
ε Ari A
ε Ari B

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]

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]

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  8. ^ a b Cite error: The named reference mnras374_3_965 was invoked but never defined (see the help page).