13_Ceti
13 Ceti
Star in the constellation Cetus
13 Ceti is a triple star system[5] in the equatorial constellation of Cetus. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.20.[2] The system is located at a distance of approximately 69 light years from the Sun based on stellar parallax, and is drifting further away with a radial velocity of +10.4 km/s.[7] It shares a common motion with the Hyades moving group,[5] although it is too old to be a member.[11]
This star was identified as a visual binary system by G. W. Hough in 1844 and given the identifier HO 212.[12] The pair have an orbital period of 6.9 years and an eccentricity of 0.77.[8] The brighter member, designated component A, is an F-type main-sequence star with a stellar classification of F6 V[4] and a visual magnitude of 5.61.[3] It appears to have an active chromosphere and is classified as an RS Canum Venaticorum variable with a variable star designation of BU Cet.[6] The star was detected as a source of soft X-ray emission by EXOSAT.[13] It has 18%[5] more mass than the Sun and is estimated to be about four[2] billion years old.
In 1907, E. B. Frost discovered the primary is a spectroscopic binary, making this a triple star system. This is a double-lined spectroscopic binary with a period of 2.1 days and a circularized orbit. The companion signature was confirmed using the separated fringe packet technique with the CHARA array.[14] It is most likely a K-type main-sequence star with a class of K3.5 V and 70% of the mass of the Sun.[5]
The secondary member of the visual binary, designated component B, is a G-type main-sequence star with a class of G4 V.[4] It has 90%[5] of the Sun's mass and a visual magnitude of 6.90.[3] A distant visual companion to this system was detected by S. W. Burnham in 1877. Designated component C, this star is a background object[15] of magnitude 12.50. As of 1999, it was located at an angular separation of 24.0″ from the primary along a position angle of 322°.[3]