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Delta Eridani

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δ Eridani
Location of δ Eridani (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Eridanus
Right ascension 03h 43m 14.90088s[1]
Declination –09° 45′ 48.2084″[1]
Apparent magnitude (V) 3.51 - 3.56[2]
Characteristics
Evolutionary stage Subgiant
Spectral type K0 IV[3]
U−B color index +0.69[4]
B−V color index +0.92[4]
Variable type Suspected RS CVn[2]
Astrometry
Radial velocity (Rv)−6.28±0.09[5] km/s
Proper motion (μ) RA: −93.16[1] mas/yr
Dec.: +743.64[1] mas/yr
Parallax (π)110.61 ± 0.29 mas[1]
Distance29.49 ± 0.08 ly
(9.04 ± 0.02 pc)
Absolute magnitude (MV)3.77[6]
Details[7]
Mass1.33±0.07[8] M☉
Radius2.35±0.01 R☉
Luminosity3.17±0.09 L☉
Surface gravity (log g)3.66±0.1 cgs
Temperature5,027±48 K
Metallicity [Fe/H]+0.07±0.03 dex
Rotational velocity (v sin i)0.7±0.6[8] km/s
Age6.194[9] Gyr
Other designations
Rana, δ Eridani, 23 Eridani, del Eri, NSV 1246, BD−10°728, GJ 150, HD 23249, HIP 17378, HR 1136, SAO 130686, LHS 1581[10]
Database references
SIMBADdata

Delta Eridani, which is Latinized from δ Eridani, is the fifth-brightest star in the constellation of Eridanus.

The star is visible to the naked eye and has been observed to vary slightly in brightness between magnitudes 3.51 and 3.56,[2] although subsequent observations did not bear this out.[11] It is relatively near to the Sun, with a distance of about 29.5 light years as determined from parallax.[1] The star is drifting closer with a radial velocity of −6 km/s.[5]

Delta Eridani is sometimes called Rana:[12] Rana means "the frog" in Latin, but derivation of this name is uncertain. The name was approved by the International Astronomic Union on 4 April 2022.[13]

Structure

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The stellar classification of this star is K0 IV,[3] matching a subgiant star that has exhausted its core hydrogen. This has caused the star to expand and become cooler than a comparable main sequence star. Stellar modelling indicates it is near the end of the subgiant stage and about to transition into a giant. It is an estimated six[9] billion years old with 33% more mass than the Sun.[8] The star has 2.35 times the size of the Sun and is radiating three times the Sun's luminosity from its photosphere at an effective temperature of 5,022 K.[7]

Delta Eridani is catalogued as a suspected RS Canum Venaticorum variable in 1983,[14] but the activity level for the star is so low that this is considered doubtful. This class of variables occurs in close binary systems. A low projected rotational velocity of under 1 km/s and the lack of radial velocity variation suggests that this putative variable is being viewed from nearly pole-on. However, an examination of the star using interferometry does not detect the presence of a companion at the expected distance.[9]

Chinese name

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In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of δ Eridani, γ 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.[15] Consequently, the Chinese name for δ Eridani itself is 天苑三 (Tiān Yuàn sān, English: the Third Star of Celestial Meadows.)[16]

See also

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References

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  1. ^ a b c d e f van Leeuwen, F. (2007). "HIP 17378". Hipparcos, the New Reduction. Retrieved 2009-12-11.
  2. ^ a b c Samus', N. N; et al. (2017). "General catalogue of variable stars". Astronomy Reports. GCVS 5.1. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  3. ^ a b Spinrad, Hyron; Taylor, Benjamin J. (1969). "Scanner Abundance Studies. I. an Investigation of Supermetallicity in Late-Type Evolved Stars". Astrophysical Journal. 157: 1279. Bibcode:1969ApJ...157.1279S. doi:10.1086/150154.
  4. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. ^ a b Jofré, E.; et al. (2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics. 574: A50. arXiv:1410.6422. Bibcode:2015A&A...574A..50J. doi:10.1051/0004-6361/201424474. S2CID 53666931.
  6. ^ Pizzolato, N.; et al. (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics. 361: 614–628. Bibcode:2000A&A...361..614P.
  7. ^ a b Rains, Adam D.; et al. (April 2020). "Precision angular diameters for 16 southern stars with VLTI/PIONIER". Monthly Notices of the Royal Astronomical Society. 493 (2): 2377–2394. arXiv:2004.02343. Bibcode:2020MNRAS.493.2377R. doi:10.1093/mnras/staa282.
  8. ^ a b c Bruntt, H.; et al. (July 2010). "Accurate fundamental parameters for 23 bright solar-type stars". Monthly Notices of the Royal Astronomical Society. 405 (3): 1907–1923. arXiv:1002.4268. Bibcode:2010MNRAS.405.1907B. doi:10.1111/j.1365-2966.2010.16575.x. S2CID 118495267.
  9. ^ a b c Thévenin, F.; et al. (June 2005). "VLTI/VINCI diameter constraints on the evolutionary status of δ Eri, ξ Hya, η Boo". Astronomy and Astrophysics. 436 (1): 253–262. arXiv:astro-ph/0501420. Bibcode:2005A&A...436..253T. doi:10.1051/0004-6361:20042075. S2CID 118169489.
  10. ^ "Del Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-11.
  11. ^ Eaton, J. A.; Poe, C. H. (April 1985). "Limits on the Variability of epsilon Eridani and delta Eridani". Information Bulletin on Variable Stars. 2712: 1. Bibcode:1985IBVS.2712....1E.
  12. ^ Bečvář, A. (1951). Atlas Coeli Skalnaté Pleso II - Katalog 1950.0. Přírodovědecké Vydavatelstrí. p. 277. Retrieved 27 May 2019.
  13. ^ "Naming Stars".
  14. ^ Fisher, G. F.; et al. (January 1983). "Delta Eridani: a Very Bright New Variable Star". Information Bulletin on Variable Stars. 2259: 1. Bibcode:1983IBVS.2259....1F.
  15. ^ (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.
  16. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived January 30, 2011, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
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