Gamma Ceti

Gamma Ceti
Diagram showing star positions and boundaries of the Cetus constellation and its surroundings
Location of γ Ceti (circled) near the center
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 02h 43m 18.03910s[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[1] mas
Distance80 ± 1 ly
(24.4 ± 0.4 pc)
Absolute magnitude (MV)+1.53[5]
Details
γ Cet A
Radius1.9[6] R☉
Luminosity21[5] L☉
Surface gravity (log g)3.96[7] cgs
Temperature8,673[7] K
Metallicity [Fe/H]0.00[7] dex
Rotational velocity (v sin i)186[8] km/s
Age300[9] Myr
Other designations
γ Cet, 86 Ceti, BD+02 422, HD 16970, HIP 12706, HR 804, SAO 110707, WDS 02433+0314.[10]
Database references
SIMBADdata

Gamma Ceti (γ Ceti, abbreviated Gam 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 (also named Kaffaljidhma[11]), 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).[12]

Gamma Ceti bore the traditional names of Al Kaff al Jidhmah, or Kaffaljidhma, derived from the Arabic الكف الجذماء meaning "The cut-short hand".[13] According to a 1971 NASA memorandum, Al Kaff al Jidhmah was originally the title for five stars: Gamma Ceti as Kafaljidma, Xi¹ Cet 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).[14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[16] It approved the name Kaffaljidhma for the component Gamma Ceti A on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.[11]

In Chinese, 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, Gamma Ceti itself is known as 天囷八 (Tiān Qūn bā, English: the Eighth Star of Circular Celestial Granary).[17]

Properties

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 a visual magnitude 3.6, A-type main sequence star with a stellar classification of A3 V. 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 a classification of K5. The luminosity class of this last component remains undetermined.[3] It shares a common proper motion with A.[18]

The measured angular diameter of the primary star is 0.74 ± 0.08 mas.[20] At the estimated distance of this system, this yields a physical size of about 1.9 times the radius of the Sun.[6] The secondary component of this system is an X-ray source with a luminosity of 2.2 × 1029 erg s−1.[21] Gamma Ceti is about 300[9] million years old and it appears to be a member of the stream of stars loosely associated with the Ursa Major moving group.[22] The primary has been examined for an excess of infrared emission that would suggest the presence of circumstellar matter, but none was found.[9]

References

  1. 1 2 3 4 5 6 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. 1 2 3 4 Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J
  3. 1 2 3 4 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
  4. ↑ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W
  5. 1 2 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.
  6. 1 2 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1 . The radius (R*) is given by:
  7. 1 2 3 Gray, R. O.; et al. (2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–70, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637.
  8. ↑ 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
  9. 1 2 3 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
  10. ↑ "gam Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-04.
  11. 1 2 "Naming Stars". IAU.org. Retrieved 16 December 2017.
  12. ↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  13. ↑ Allen, Richard Hinckley (1963), Star Names: Their Lore and Meaning (Dover ed.), University of Chicago, p. 160
  14. ↑ Rhoads, Jack W. (November 15, 1971), Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars (PDF), Jet Propulsion Laboratory, California Institute of Technology
  15. ↑ "International Astronomical Union | IAU". www.iau.org. Retrieved 2017-04-01.
  16. ↑ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  17. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日
  18. 1 2 "Washington Double Star Catalog". United States Naval Observatory. Retrieved 2 January 2018.
  19. ↑ Mollise, Rod (2006), The urban astronomer's guide: a walking tour of the cosmos for city sky watchers, Patrick Moore's practical astronomy series, Springer, p. 200, ISBN 1-84628-216-0
  20. ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
  21. ↑ 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
  22. ↑ 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
  • Kaler, James B., "KAFFALJIDHMA (Gamma Ceti)", Stars, University of Illinois, retrieved 2012-03-04
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.