Location of γ Eridani (circled) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 03 58 01.76695 |
| Declination | −13° 30′ 30.6698″ |
| Apparent magnitude (V) | 2.88 - 2.96 |
| Characteristics | |
| Evolutionary stage | AGB |
| Spectral type | M0III-IIIb |
| U−B color index | +1.96 |
| B−V color index | +1.58 |
| Variable type | Lb? |
| Astrometry | |
| Radial velocity (Rv) | 60.81±0.25 km/s |
| Proper motion (μ) | RA: +61.57 mas/yr Dec.: −113.11 mas/yr |
| Parallax (π) | 17.0016 ± 0.2254 mas |
| Distance | 192 ± 3 ly (58.8 ± 0.8 pc) |
| Absolute magnitude (MV) | −1.19 |
| Details | |
| Mass | 1.55 M☉ |
| Radius | 58.7±0.8 R☉ |
| Luminosity | 566 L☉ |
| Surface gravity (log g) | 1.18 cgs |
| Temperature | 3,875±129 K |
| Rotational velocity (v sin i) | 3.8 km/s |
| Other designations | |
| Zaurac, Gamma Eridani, Gamma Eri, γ Eridani, γ Eri, 34 Eridani, 34 Eri, HD 25025, HIP 18543, HR 1231 | |
| Database references | |
| SIMBAD | data |
Gamma Eridani (γ Eridani, abbreviated Gamma Eri, γ Eri), formally named Zaurak /ˈzɔːræk/, 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.
Description
Gamma Eridani has been defined as a standard star for the spectral class M0III-IIIb. It is a red giant on the asymptotic giant branch, fusing hydrogen and helium in separate shells outside its core. Observations published in 1960 showed it to vary in brightness by a few hundredths of a magnitude. In 1977, it was officially listed as a variable star in the General Catalogue of Variable Stars although the class of variable is uncertain.
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.
Nomenclature
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'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 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, τ Eridani, τ Eridani, τ Eridani, τ Eridani, τ Eridani, τ Eridani, τ Eridani, τ Eridani and τ Eridani. Consequently, the Chinese name for γ Eridani itself is 天苑一 (Tiān Yuàn yī, English: the First of Celestial Meadows.)
USS Zaurak (AK-117) was a United States Navy Crater class cargo ship named after the star.
References
- ^ 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.
- ^ Samus, N. N.; Durlevich, O. V.; et al. (2007), Combined General Catalogue of Variable Stars (GCVS4.2). VizieR On-line Data Catalog: B/gcvs.
- ^ Eggen, O. J. (1992), "Asymptotic giant branch stars near the sun", The Astronomical Journal, 104: 275, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
- ^ 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.
- ^ Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
- ^ 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.
- 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.
- 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.
- ^ 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.
- 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.
- "* gam Eri", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2016-10-09.
- 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.
- IAU Catalog of Star Names, retrieved 28 July 2016.
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- Cousins, A. W. J. (1960), "New Bright Variable Stars", Monthly Notes of the Astronomical Society of Southern Africa, 19: 56, Bibcode:1960MNSSA..19...56C.
- 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.
- 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.
- Allen, R. H. (1963), Star Names, Dover, p. 218, retrieved 2016-10-09.
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- (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.
- (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.
