Τ4_Eridani
Tau4 Eridani
Binary star system in the constellation Eridanus
Tau4 Eridani (τ4 Eridani, τ4 Eri) is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.65.[2] The distance to this star can be estimated using the parallax method, which yields a value of roughly 300 light years.[1]
This is an evolved red giant star currently on the asymptotic giant branch[3] with a stellar classification of M3/4 III.[4] It is a slow irregular variable star of type Lb, undergoing changes in magnitude over the range 3.57−3.72[5] with a periodicity of 23.8 d.[13] The measured angular diameter of Tau4 Eridani is 10.58±1.00 mas.[14] At its estimated distance, this yields a physical size of about 106 times the radius of the Sun.[10] It shines with 1,537[11] times the luminosity of the Sun from an outer atmosphere at an effective temperature of 3,712 K.[9]
This is most likely a binary star system.[15] The companion is a magnitude 9.5 star at an angular separation of 5.7″ along a position angle of 291°, as of 2013.[16]