13 Ceti
{{short description|Star in the constellation Cetus}}
{{Starbox begin}}
{{Starbox image
| image = 250px
| caption = A light curve for BU Ceti, plotted from TESS data
}}
{{Starbox observe
| epoch = J2000.0
| constell = Cetus
| dec = {{DEC|−03|35|34.2367}}
| appmag_v = 5.20 {{nowrap|(5.61 + 6.90)}}
}}
{{Starbox character
| type = Main sequence
| class = {{nowrap|F6 V + G4 V + K3.5 V}}
| u-b =
| variable = RS CVn
}}
{{Starbox astrometry
| radial_v = {{val|+10.37|0.40}}
| parallax = 47.05
| p_error = 0.67
}}
{{Starbox orbit
| primary = A
| name = B
| period_unitless = {{val|2516.6163|2.7808|u=days|fmt=commas}}
| eccentricity = 0.77300
| periastron = {{val|56935.2034|u=MJD|fmt=commas}}
| periarg = 283.8°
}}
{{Starbox orbit
| primary = Aa
| name = Ab
| period_unitless = {{val|2.081891|0.000005|u=days|fmt=commas}}
| axis_unitless = {{val|1.260|0.010|u=Mm|p=≥}}
| eccentricity = 0.0 (fixed)
| periastron = {{val|2443400.4573|0.0032|u=HJD|fmt=commas}}
| periarg = 0.0
| k1 = {{val|43.98|0.39}}
}}
{{Starbox detail
| component1 = Aa
| radius =
| gravity =
| metal_fe =
| rotation =
| rotational_velocity =
| age_gyr = {{val|3.8|1.8|0.3}}
| component2 = B
}}
{{Starbox catalog
| names = {{odlist | V=BU Cet | name=HO 212 | F=13 Cet | BD=−04°62 | GJ=23 | HD=3196 | HIP=2762 | HR=142 | SAO=128839 | WDS=00352-0336 | GC=696 | NSV=212 }}
}}
{{Starbox reference
| Simbad = 13+Cet
}}
{{Starbox end}}
13 Ceti is a triple star system in the equatorial constellation of Cetus. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.20. 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. It shares a common motion with the Hyades moving group, although it is too old to be a member.
This star was identified as a visual binary system by G. W. Hough in 1844 and given the identifier HO 212. The pair have an orbital period of {{convert|2516.6163|days|years|1|disp=out|abbr=off}} and an eccentricity of 0.77. The brighter member, designated component A, is an F-type main-sequence star with a stellar classification of F6 V and a visual magnitude of 5.61. It appears to have an active chromosphere and is classified as an RS Canum Venaticorum variable with a variable star designation of BU Cet. The star was detected as a source of soft X-ray emission by EXOSAT. It has 18% more mass than the Sun and is estimated to be about four 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. 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.
The secondary member of the visual binary, designated component B, is a G-type main-sequence star with a class of G4 V. It has 90% of the Sun's mass and a visual magnitude of 6.90. A distant visual companion to this system was detected by S. W. Burnham in 1877. Designated component C, this star is a background object of magnitude 12.50. As of 1999, it was located at an angular separation of {{val|24.0|ul=arcsecond}} from the primary along a position angle of 322°.
References
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}}
{{Stars of Cetus|state=collapsed}}
{{DEFAULTSORT:13 Ceti}}
Category:F-type main-sequence stars
Category:G-type main-sequence stars
Category:K-type main-sequence stars
Category:RS Canum Venaticorum variables