111 Tauri
Wide binary star system in the constellation Taurus
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111 Tauri is a wide binary star[5] system in the constellation Taurus. It is located at a distance of 48 light years from the Sun. Primary component A is a main sequence star with a stellar classification of F8V. The secondary component B (Gliese 201) is a K-type main sequence star.[5] The primary is larger and more luminous than the Sun, with about 130% of the Sun's radius and 185% of the Sun's luminosity. The apparent magnitude of 5.0 indicates it is a faint star that can be viewed by the naked eye under good, dark-sky conditions.
The metallicity of the primary star, which measures the proportion of elements other than hydrogen and helium, is similar to the Sun. Estimates of [Fe/H], which is the logarithm of the ratio of iron to hydrogen as compared to the Sun, range from a low of −0.14 to a high of 0.05.[11][19] This star shows an unusually high content of lithium, which remains unexplained.[19] Age estimates for this star range from 3.6 to 3.76 billion years.[8][20] however the most recent age determination indicates a very young star with an age of 20 to 50 million years.[14] It is a prominent X-ray source.[19]
This star is rotating relatively rapidly, completing a rotation along the equator every 3.5 days[12] as compared to 25 days for the Sun. It is also undergoing differential rotation in which the rotation velocity varies by latitude.[21] In 1996, Kazimierz Stępień and Edward H. Geyer announced that 111 Tauri is a variable star.[22] It is a BY Draconis variable, and was given the variable star designation V1119 Tauri, in 1997.[23][24]
This star was examined for an excess of infrared emission that could indicate it has a circumstellar debris disk of dust, but no significant excess was observed.[20] The space velocity components of this star are [U, V, W] = [−36.94, −14.63, 7.63] km/s.[25] It is a member of the Hyades stellar kinematic group of co-moving stars.[19]