Epsilon Arietis


Epsilon 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, 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 from the brighter component, along a position angle of, is the magnitude 5.5 companion. Both are A-type main sequence stars with a stellar classification of A2 Vs. 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.

Name

This star system, along with δ Ari, ζ Ari, π Ari, and ρ3 Ari, were Al Bīrūnī's Al Buṭain, 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 and ζ Ari as Al Buṭain IV
In Chinese astronomy, Epsilon Arietis may be or may be part of Tso Kang.