13 Ceti
Star in the constellation Cetus
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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.[1] 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.[8] It shares a common motion with the Hyades moving group,[5] although it is too old to be a member.[13]
| Aa, F6V | |||||||||||||
| 2.1 days | |||||||||||||
| Ab, K3.5V | |||||||||||||
| 6.9 years | |||||||||||||
| B, G4V | |||||||||||||
Hierarchy of orbits in the 13 Ceti system[11]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cetus[1] |
| Right ascension | 00h 35m 14.87968s[2] |
| Declination | −03° 35′ 34.2367″[2] |
| Apparent magnitude (V) | 5.20[1] (5.61 + 6.90)[3] |
| Characteristics | |
| B−V color index | 0.567±0.008[1] |
| A | |
| Evolutionary stage | Main sequence[4] + main sequence[5] |
| Spectral type | F6 V + K3.5 V[6] |
| Variable type | RS CVn[7] |
| B | |
| Evolutionary stage | Main sequence[4] |
| Spectral type | G4 V[6] |
| Astrometry | |
| Radial velocity (Rv) | +10.37±0.40[8] km/s |
| Proper motion (μ) | RA: +408.34[2] mas/yr Dec.: −35.22[2] mas/yr |
| Parallax (π) | 47.05±0.67 mas[2] |
| Distance | 69.3 ± 1.0 ly (21.3 ± 0.3 pc) |
| Absolute magnitude (MV) | 3.56[1] |
| Orbit[4] | |
| Primary | A |
| Name | B |
| Period (P) | 6.8975+0.0005 −0.0006 yr |
| Semi-major axis (a) | 234.07+0.74 −0.73 mas |
| Eccentricity (e) | 0.7615+0.0013 −0.0014 |
| Inclination (i) | 47.83±0.24° |
| Longitude of the node (Ω) | 328.39±0.22° |
| Periastron epoch (T) | 1890.6139+0.0091 −0.0085 |
| Argument of periastron (ω) (secondary) | 104.70±0.18° |
| Semi-amplitude (K1) (primary) | 11.68±0.51 km/s |
| Semi-amplitude (K2) (secondary) | 15.59±0.17 km/s |
| Orbit[9] | |
| Primary | Aa |
| Name | Ab |
| Period (P) | 2.081891±0.000005 d |
| Semi-major axis (a) | ≥1.260±0.010 Mm |
| Eccentricity (e) | 0.0 (fixed) |
| Periastron epoch (T) | 2,443,400.4573±0.0032 HJD |
| Argument of periastron (ω) (secondary) | 0.0° |
| Semi-amplitude (K1) (primary) | 43.98±0.39 km/s |
| Details | |
| Aa | |
| Mass | 1.18±0.09[5] M☉ |
| Luminosity | 2.63[10] L☉ |
| Temperature | 6,457[10] K |
| Age | 3.8+1.8 −0.3[1] Gyr |
| Ab | |
| Mass | 0.35[11] M☉ |
| B | |
| Mass | 0.90±0.09[5] M☉ |
| Luminosity | 0.83[10] L☉ |
| Temperature | 5,754[10] K |
| Age | 2.5[10] Gyr |
| Other designations | |
| HO 212, 13 Cet, BU Cet, BD−04°62, GC 696, GJ 23, HD 3196, HIP 2762, HR 142, SAO 128839, WDS 00352-0336[12] | |
| Database references | |
| SIMBAD | data |
This star was identified as a visual binary system by G. W. Hough in 1844 and given the identifier HO 212.[14] The pair have an orbital period of 6.9 years and an eccentricity of 0.76.[4] The brighter member, designated component A, is an F-type main-sequence star with a stellar classification of F6 V[6] 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.[7] The star was detected as a source of soft X-ray emission by EXOSAT.[15] It has 18% more mass than the Sun[5] and is estimated to be about four billion years old.[1]
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.[16] 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.[6] 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[17] 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]