13 Ceti

A light curve for BU Ceti, plotted from TESS data
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 00h 35m 14.87968s[1]
Declination −03° 35′ 34.2367″[1]
Apparent magnitude (V) 5.20[2] (5.61 + 6.90)[3]
Characteristics
Evolutionary stage Main sequence
Spectral type F6 V + G4 V + K3.5 V[4][5]
B−V color index 0.567±0.008[2]
Variable type RS CVn[6]
Astrometry
Radial velocity (Rv)+10.37±0.40[7] km/s
Proper motion (μ) RA: +408.34[1] mas/yr
Dec.: −35.22[1] mas/yr
Parallax (π)47.05 ± 0.67 mas[1]
Distance69.3 ± 1.0 ly
(21.3 ± 0.3 pc)
Absolute magnitude (MV)3.56[2]
Orbit[8]
PrimaryA
CompanionB
Period (P)2,516.6163±2.7808 d
Eccentricity (e)0.77300
Periastron epoch (T)56,935.2034 MJD
Argument of periastron (ω)
(secondary)		283.8°°
Orbit[9]
PrimaryAa
CompanionAb
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
Mass1.18±0.09[5] M☉
Luminosity2.63[8] L☉
Temperature6,457[8] K
Age3.8+1.8
−0.3[2] Gyr
B
Mass0.90±0.09[5] M☉
Luminosity0.83[8] L☉
Temperature5,754[8] K
Age2.5[8] Gyr
Other designations
HO 212, 13 Cet, BU Cet, NSV 212, BD−04°62, GC 696, GJ 23, HD 3196, HIP 2762, HR 142, SAO 128839, WDS 00352-0336[10]
Database references
SIMBADdata

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]

References

  1. 1 2 3 4 5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  2. 1 2 3 4 5 6 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  3. 1 2 3 4 Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22.
  4. 1 2 3 Strassmeier, K. G.; et al. (July 1993), "A catalog of chromospherically active binary stars", Astronomy and Astrophysics, Supplemental Series (2nd ed.), 100: 173–225, Bibcode:1993A&AS..100..173S.
  5. 1 2 3 4 5 6 7 8 Andrade, Manuel (October 2019), "Colour-dependent accurate modelling of dynamical parallaxes and masses of visual binaries. Application to the VB+SB2 systems with definitive orbits", Astronomy & Astrophysics, 630: 11, Bibcode:2019A&A...630A..96A, doi:10.1051/0004-6361/201936199, A96.
  6. 1 2 Fernandez-Figueroa, M. J.; et al. (January 1994), "CA II H and K and H alpha Emissions in Chromospherically Active Binary Systems (RS Canum Venaticorum and BY Draconis)" (PDF), Astrophysical Journal Supplement, 90: 433, Bibcode:1994ApJS...90..433F, doi:10.1086/191866.
  7. 1 2 Karataș, Yüksel; et al. (2004), "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution", Monthly Notices of the Royal Astronomical Society, 349 (3): 1069–1092, arXiv:astro-ph/0404219, Bibcode:2004MNRAS.349.1069K, doi:10.1111/j.1365-2966.2004.07588.x, S2CID 15290475.
  8. 1 2 3 4 5 6 7 Piccotti, Luca; et al. (February 2020), "A study of the physical properties of SB2s with both the visual and spectroscopic orbits", Monthly Notices of the Royal Astronomical Society, 492 (2): 2709–2721, Bibcode:2020MNRAS.492.2709P, doi:10.1093/mnras/stz3616.
  9. ↑ Duquennoy, A.; Mayor, M. (1991), "Multiplicity among solar-type stars in the solar neighbourhood. II - Distribution of the orbital elements in an unbiased sample", Astronomy and Astrophysics, 248 (2): 485–524, Bibcode:1991A&A...248..485D.
  10. ↑ "13 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-11-05.
  11. ↑ Montes, D.; et al. (2001), Garcia Lopez, Ramon J.; et al. (eds.), "Chromospherically Active Binaries Members of Young Stellar Kinematic Groups (CD-ROM Directory: contribs/montes2)", 11th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun, ASP Conference Proceedings, San Francisco: Astronomical Society of the Pacific, vol. 223, p. 1477, arXiv:astro-ph/9912161, Bibcode:2001ASPC..223.1477M.
  12. ↑ Bauer, Carl August (November 1944), "A Report on New Spectrographic Material of 13 Ceti", Astrophysical Journal, 100: 302, Bibcode:1944ApJ...100..302B, doi:10.1086/144671.
  13. ↑ Bedford, D. K.; et al. (February 1985), "X-Ray Observations of Active Chromosphere Stars", Space Science Reviews, 40 (1–2): 51–54, Bibcode:1985SSRv...40...51B, doi:10.1007/BF00212865, S2CID 121806441.
  14. ↑ Raghavan, Deepak; et al. (January 2012), "A Search for Separated Fringe Packet Binaries Using the CHARA Array", The Astrophysical Journal, 745 (1): 10, Bibcode:2012ApJ...745...24R, doi:10.1088/0004-637X/745/1/24, S2CID 15622813, 24.
  15. ↑ Pogo, A. (September 1928), "Spectrographic study of the multiple system HO 212 = 13 Ceti AB.", Astrophysical Journal, 68: 116−144, Bibcode:1928ApJ....68..116P, doi:10.1086/143133.
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