Gamma Ceti

γ Ceti

Location of γ Ceti (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cetus
Right ascension	02^h 43^m 18.03910^s[1]
Declination	+03° 14′ 08.9390″[1]
Apparent magnitude (V)	3.47[2] (3.56/6.63/10.16)[3]
Characteristics
Spectral type	A3 V + F3 V + K5[3]
U−B color index	+0.07[2]
B−V color index	+0.09[2]
Astrometry
Radial velocity (Rv)	–5.1[4] km/s
Proper motion (μ)	RA: –146.10[1] mas/yr Dec.: –146.12[1] mas/yr
Parallax (π)	40.97 ± 0.63 mas[1]
Distance	80 ± 1 ly (24.4 ± 0.4 pc)
Absolute magnitude (MV)	+1.53[5]
Details
γ Cet A
Mass	1.88[6] M☉
Radius	1.9[7] R☉
Luminosity	21[5] L☉
Surface gravity (log g)	4.3[8] cgs
Temperature	8,551[8] K
Metallicity [Fe/H]	0.00[9] dex
Rotational velocity (v sin i)	186[10] km/s
Age	647[8] Myr
γ Cet B
Mass	1.17[6] M☉
Temperature	6,051[8] K
Rotational velocity (v sin i)	10[8] km/s
Other designations
Kaffaljidhma, γ Cet, 86 Ceti, BD+02 422, HD 16970, HIP 12706, HR 804, SAO 110707, WDS 02433+0314[11]
Database references
SIMBAD	Gamma Ceti system
	A
	B
	C

Gamma Ceti (γ Ceti, abbreviated Gamma Cet, γ Cet) is a triple star system in the equatorial constellation of Cetus. It has a combined apparent visual magnitude of 3.47.^[2] Based upon parallax measurements, this star is located at a distance of about 80 light-years (24.4 parsecs) from the Sun.^[1]

The three components are designated Gamma Ceti A (officially named Kaffaljidhma /ˌkæfəlˈdʒɪdmə/, the traditional name for the entire system),^[12] B and C.

Nomenclature

γ Ceti (Latinised to Gamma Ceti) is the system's Bayer designation. The designations of the three components as Gamma Ceti A, B and C derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).^[13] The close pair AB is also designated HIP 12706, HD 16970, and HR 804. The system of A, B, and C is collectively designated GJ 106.1 in the Gliese Catalogue of Nearby Stars.

Gamma Ceti bore the traditional names of Al Kaff al Jidhmah or Kaffaljidhma, derived from Arabic: الكف الجذماء al-kaf al-jaðmāʾ ('the cut-short hand').^[14] According to a 1971 NASA memorandum, Al Kaff al Jidhmah was originally the title for five stars: Gamma Ceti as Kafaljidma, Xi¹ Ceti as Al Kaff al Jidhmah I, Xi² Ceti as Al Kaff al Jidhmah II, Delta Ceti as Al Kaff al Jidhmah III and Mu Ceti as Al Kaff al Jidhmah IV (excluding Alpha Ceti and Lambda Ceti).^[15] The IAU Working Group on Star Names (WGSN)^[16] approved the name Kaffaljidhma for the component Gamma Ceti A on February 1, 2017.^[12]

In Chinese astronomy, 天囷 Tiān Qūn, meaning 'Circular Celestial Granary', refers to an asterism consisting of Gamma Ceti, Alpha Ceti, Kappa¹ Ceti, Lambda Ceti, Mu Ceti, Xi¹ Ceti, Xi² Ceti, Nu Ceti, Delta Ceti, 75 Ceti, 70 Ceti, 63 Ceti and 66 Ceti. Consequently, the Chinese name for Gamma Ceti itself is 天囷八 Tiān Qūn bā ('the Eighth Star of Circular Celestial Granary').^[17]

Triple system

Gamma Ceti appears to be a triple star system.^[18] The inner pair (A and B) have an angular separation of 2.6 arcseconds. The primary component of this pair (A) is an A-type main sequence star with a stellar classification of A3 V and a visual magnitude of 3.6. The fainter secondary component (B) is an F-type main sequence star that has a classification of F3 V and a magnitude of 6.6.^[3] The contrasting colors of these two stars makes them a popular target of amateur astronomers. The two can be resolved with a small, 4 in (10 cm) aperture telescope under ideal seeing conditions, although at times they can be a challenge to resolve even with a much larger scope.^[19]

At a wide separation of 840 arcseconds is component C, a dim, magnitude 10.2 K-type star with the designation BD+02 418.^[3] It shares a common proper motion with A and is at a very similar distance,^[20][18] but is separated from the close pair by over 20,000 au.^[21] It has a spectral classification of K5V.^[22] There are several other stars brighter and closer to Gamma Ceti than BD+02 418 – BD+02 419, HD 16985, and TYC 50-1274-1 – but they are all more distant background stars.

Properties

The measured angular diameter of the primary star is 0.74 ± 0.08 mas.^[23] At the estimated distance of this system, this yields a physical size of about 1.9 times the radius of the Sun.^[7] The secondary component of this system is an X-ray source with a luminosity of 2.2 × 10²⁹ erg s⁻¹.^[24] Gamma Ceti is about 300 million years old,^[25] and it appears to be a member of the stream of stars loosely associated with the Ursa Major Moving Group.^[26] The primary has been examined for an excess of infrared emission that would suggest the presence of circumstellar matter, but none was found.^[25]

References

1. van Leeuwen, F. (November 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.
2. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (1): 99–110. Bibcode:1966CoLPL...4...99J.
3. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
4. Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W.
5. Anderson, E.; Francis, Ch. (25 May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
6. Tokovinin, A.; Kiyaeva, O. (21 February 2016). "Eccentricity distribution of wide binaries". Monthly Notices of the Royal Astronomical Society. 456 (2): 2070–2079. arXiv:1512.00278. Bibcode:2016MNRAS.456.2070T. doi:10.1093/mnras/stv2825.
7. Lang, Kenneth R. (February 2006). Astrophysical Formulae: Volume I & Volume II: Radiation, Gas Processes and High Energy Astrophysics/Space, Time, Matter and Cosmology. Astronomy and Astrophysics Library. Vol. 1 (3 ed.). Springer Science & Business Media. p. 41. ISBN 978-3-540-29692-8.
   The radius (R_*) is given by:

   ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(24.4\cdot 0.74\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 3.88\cdot R_{\bigodot }\end{aligned}}}$

8. Gullikson, Kevin; Kraus, Adam; Dodson-Robinson, Sarah (26 July 2016). "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars". The Astronomical Journal. 152 (2): 40–53. arXiv:1604.06456. Bibcode:2016AJ....152...40G. doi:10.3847/0004-6256/152/2/40. S2CID 119179065.
9. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Robinson, P. E. (11 July 2003). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I". The Astronomical Journal. 126 (4): 2048–2059. arXiv:astro-ph/0308182. Bibcode:2003AJ....126.2048G. doi:10.1086/378365.
10. Royer, F.; Zorec, J.; Gómez, A. E. (February 2007). "Rotational velocities of A-type stars: III. Velocity distributions". Astronomy and Astrophysics. 463 (2): 671–682. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224. S2CID 18475298.
11. "gam Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-04.
12. "Naming Stars". International Astronomical Union. Archived from the original on 2017-12-22. Retrieved 16 December 2017.
13. Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (3 December 2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
14. Allen, Richard Hinckley (1963) [1899]. Star Names: Their Lore and Meaning. New York, NY: Dover Publications. p. 160. ISBN 0-486-21079-0 – via LacusCurtius.
15. Rhoads, Jack W. (15 November 1971). Technical Memorandum 33-507: A reduced star catalog containing 537 named stars (PDF). Jet Propulsion Laboratory (Report). NASA. NASA-CR-124573. Archived from the original (PDF) on 2019-06-12. Retrieved 2018-02-03.
16. "Division C WG Star Names". International Astronomical Union. Archived from the original on 2017-08-02. Retrieved 2017-04-01.
17. 陳冠中; 陳輝樺 (11 July 2006). "中國古代的星象系統 (72): 胃宿天區". AEEA 天文教育資訊網 [AEEA (Activities of Exhibition and Education in Astronomy)] (in Chinese). National Museum of Natural Science. Archived from the original on 2020-10-02.
18. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I. (2 October 2008). "Washington Double Star Catalog". United States Naval Observatory. Archived from the original on 14 February 2011. Retrieved 2 January 2018.
19. Mollise, Rod (May 2006). The Urban Astronomer's Guide: A Walking Tour of the Cosmos for City Sky Watchers. The Patrick Moore Practical Astronomy Series. Springer Science & Business Media. p. 200. ISBN 978-1-84628-216-4.
20. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
21. Dhital, Saurav; West, Andrew A.; Stassun, Keivan G.; Bochanski, John J. (7 May 2010). "Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES): A Catalog of Very Wide, Low-mass Pairs". The Astronomical Journal. 139 (6): 2566–2586. arXiv:1004.2755. Bibcode:2010AJ....139.2566D. doi:10.1088/0004-6256/139/6/2566. hdl:1721.1/93136. S2CID 661494.
22. Stephenson, C. B. (July 1986). "Dwarf K and M stars of high proper motion found in a hemispheric survey". The Astronomical Journal. 92: 139–165. Bibcode:1986AJ.....92..139S. doi:10.1086/114146.
23. Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005). "CHARM2: An updated Catalog of High Angular Resolution Measurements". Astronomy and Astrophysics. 431 (2): 773–777. Bibcode:2005A&A...431..773R. doi:10.1051/0004-6361:20042039.
24. Schröder, C.; Schmitt, J. H. M. M. (November 2007). "X-ray emission from A-type stars". Astronomy and Astrophysics. 475 (2): 677–684. Bibcode:2007A&A...475..677S. doi:10.1051/0004-6361:20077429.
25. Su, K. Y. L.; et al. (December 2006). "Debris Disk Evolution around A Stars". The Astrophysical Journal. 653 (1): 675–689. arXiv:astro-ph/0608563. Bibcode:2006ApJ...653..675S. doi:10.1086/508649. S2CID 14116473.
26. King, Jeremy R.; Villarreal, Adam R.; Soderblom, David R.; Gulliver, Austin F.; Adelman, Saul J. (April 2003). "Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group". The Astronomical Journal. 125 (4): 1980–2017. Bibcode:2003AJ....125.1980K. doi:10.1086/368241 – via TigerPrints.

External links

• Information about Kaffaljidhma on STARS
• Gamma Ceti on AAS WorldWide Telescope