Wikipedia

Gamma Eridani

Gamma Eridani (γ Eridani, abbreviated Gamma Eri, γ Eri), formally named Zaurak /ˈzɔːræk/,[12][13] is a variable star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude that varies around 2.9, and lies at a distance of about 203 light years from the Sun, as determined by the Hipparcos astrometry satellite.

γ Eridani
Location of γ Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 03h 58m 01.76695s[1]
Declination −13° 30′ 30.6698″[1]
Apparent magnitude (V) 2.88 - 2.96[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M0III-IIIb[4]
U−B color index 1.96[5]
B−V color index 1.58[5]
Variable type Lb?[2]
Astrometry
Radial velocity (Rv)60.81±0.25[6] km/s
Proper motion (μ) RA:  61.57[1] mas/yr
Dec.: −113.11[1] mas/yr
Parallax (π)17.0016 ± 0.2254 mas[7]
Distance192 ± 3 ly
(58.8 ± 0.8 pc)
Absolute magnitude (MV)−1.19[8]
Details
Mass1.55[9] M☉
Radius58.7±0.8[10] R☉
Luminosity566[9] L☉
Surface gravity (log g)1.18[9] cgs
Temperature3,875±129[9] K
Rotational velocity (v sin i)3.8[6] km/s
Other designations
Zaurac, Gamma Eridani, Gamma Eri, γ Eridani, γ Eri, 34 Eridani, 34 Eri, HD 25025, HIP 18543, HR 1231[11]
Database references
SIMBADdata

Description

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A light curve for Gama Eridani, plotted from Hipparcos data[14]

Gamma Eridani has been defined as a standard star for the spectral class M0III-IIIb.[4] It is a red giant on the asymptotic giant branch, fusing hydrogen and helium in separate shells outside its core.[3] Observations published in 1960 showed it to vary in brightness by a few hundredths of a magnitude.[15] In 1977, it was officially listed as a variable star in the General Catalogue of Variable Stars although the class of variable is uncertain.[16]

The Gaia EDR3 data identified a comoving 0.1 M☉ companion star of Gamma Eridani, at a projected separation of 1000 AU. It is likely that there is an additional red dwarf companion that at a distance within 50 AU, too close to resolve from the primary.[17]

Nomenclature

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Gamma Eridani is the star's Bayer designation. It has the traditional name Zaurak, alternatively spelled Zaurac, which is one of the Persian words for 'boat'.[18] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[20] included a table of the first two batches of names approved by the WGSN; which included Zaurak for this star.

In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of γ Eridani, δ Eridani, π Eridani, ε Eridani, ζ Eridani, η Eridani, π Ceti, τ1 Eridani, τ2 Eridani, τ3 Eridani, τ4 Eridani, τ5 Eridani, τ6 Eridani, τ7 Eridani, τ8 Eridani and τ9 Eridani.[21] Consequently, the Chinese name for γ Eridani itself is 天苑一 (Tiān Yuàn yī, English: the First [Star] of Celestial Meadows.)[22]

USS Zaurak (AK-117) was a United States Navy Crater class cargo ship named after the star.

References

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  1. ^ a b c d 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. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2007), Combined General Catalogue of Variable Stars (GCVS4.2). VizieR On-line Data Catalog: B/gcvs.
  3. ^ a b Eggen, O. J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
  4. ^ a b Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  5. ^ a b Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
  6. ^ a b Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  7. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  8. ^ Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440, S2CID 12136256.
  9. ^ a b c d Ayres, Thomas (2023-05-01), "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022", The Astrophysical Journal Supplement Series, 266 (1): 6, Bibcode:2023ApJS..266....6A, doi:10.3847/1538-4365/acb535, ISSN 0067-0049 Gamma Eridani's database entry at VizieR.
  10. ^ Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R. (November 2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 162 (5): 198. arXiv:2211.09030. Bibcode:2021AJ....162..198B. doi:10.3847/1538-3881/ac2431. ISSN 0004-6256. S2CID 238998021.
  11. ^ "* gam Eri", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2016-10-09.
  12. ^ Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.), Cambridge, Massachusetts: Sky Pub, ISBN 978-1-931559-44-7.
  13. ^ IAU Catalog of Star Names, retrieved 28 July 2016.
  14. ^ "Hipparcos Tools Interactive Data Access", Hipparcos, ESA, retrieved 8 December 2021.
  15. ^ Cousins, A. W. J. (1960), "New Bright Variable Stars", Monthly Notes of the Astronomical Society of Southern Africa, 19: 56, Bibcode:1960MNSSA..19...56C.
  16. ^ Kukarkin, B. V.; Kholopov, P. N.; Fedorovich, V. P.; Kireyeva, N. N.; Kukarkina, N. P.; Medvedeva, G. I.; Perova, N. B. (1977), "62nd Name-List of Variable Stars", Information Bulletin on Variable Stars, 1248: 1, Bibcode:1977IBVS.1248....1K.
  17. ^ Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (April 2024). "Stellar and substellar companions from Gaia EDR3: Proper-motion anomaly and resolved common proper-motion pairs (Corrigendum)". Astronomy & Astrophysics. 684: C2. Bibcode:2024A&A...684C...2K. doi:10.1051/0004-6361/202450066e.
  18. ^ Allen, R. H. (1963), Star Names, Dover, p. 218, retrieved 2016-10-09.
  19. ^ IAU Working Group on Star Names (WGSN), IAU, retrieved 2016-05-22
  20. ^ Bulletin of the IAU Working Group on Star Names, No. 1 (PDF), retrieved 2016-07-28.
  21. ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  22. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 19, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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