Astronomy:Delta Eridani

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Short description: Star in the constellation Eridanus
δ Eridani / Rana
Location of δ Eridani (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Eridanus
Right ascension  03h 43m 14.90054s[1]
Declination −09° 45′ 48.2110″[1]
Apparent magnitude (V) 3.53[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 none[2]
Astrometry
Radial velocity (Rv)−6.28±0.09[5] km/s
Proper motion (μ) RA: −93.634[1] mas/yr
Dec.: +744.360[1] mas/yr
Parallax (π)110.0254 ± 0.1944[1] mas
Distance29.64 ± 0.05 ly
(9.09 ± 0.02 pc)
Absolute magnitude (MV)3.77[6]
Details[7]
Mass1.215[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[9] km/s
Age6.194[8] Gyr
Other designations
Rana, δ Eri, 23 Eridani, NSV 1246, BD−10°728, GJ 150, HD 23249, HIP 17378, HR 1136, SAO 130686, LHS 1581[10]
Database references
SIMBADdata

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

The star is visible to the naked eye with an apparent magnitude of 3.54. It is relatively near to the Sun, with a distance of about 29.6 light-years as determined from parallax.[1] The star is drifting closer with a radial velocity of −6 km/s.[5]

Nomenclature

Delta Eridani is sometimes called Rana;[11] Rana means frog in Latin. This name first appeared as Rana Secunda, the "second frog", in Giuseppe Piazzi's star catalogue; this was likely a misattributed name for Beta Ceti (Diphda), known as the "second frog" in Arabic.[12] The name Rana was approved by the IAU Working Group on Star Names on 4 April 2022.[13]

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.[14] Consequently, the Chinese name for δ Eridani itself is 天苑三 (Tiān Yuàn sān, English: the Third Star of Celestial Meadows.)[15]

Characteristics

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 billion years old[8] with 33% more mass than the Sun.[9] 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 was catalogued as a suspected RS Canum Venaticorum variable in 1983,[16] varying slightly in brightness between magnitudes 3.51 and 3.56,[17] although subsequent observations did not bear this out[18] and an examination of the star using interferometry did not detect the presence of a companion at the expected distance.[8] Thus, this classification is now considered erroneous.[19] The star has a very low level of chromospheric activity.[19] A low projected rotational velocity of under 1 km/s and the lack of radial velocity variation suggest that this star is being viewed from nearly pole-on.[8]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 "del Eri". https://www.aavso.org/vsx/index.php?view=detail.top&oid=14215. 
  3. ↑ 3.0 3.1 Spinrad, Hyron; Taylor, Benjamin J. (1969). "Scanner Abundance Studies. I. an Investigation of Supermetallicity in Late-Type Evolved Stars". Astrophysical Journal 157: 1279. doi:10.1086/150154. Bibcode: 1969ApJ...157.1279S. 
  4. ↑ 4.0 4.1 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode: 1986EgUBV........0M. 
  5. ↑ 5.0 5.1 Jofré, E. et al. (2015). "Stellar parameters and chemical abundances of 223 evolved stars with and without planets". Astronomy & Astrophysics 574: A50. doi:10.1051/0004-6361/201424474. Bibcode: 2015A&A...574A..50J. 
  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. ↑ 7.0 7.1 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. doi:10.1093/mnras/staa282. Bibcode: 2020MNRAS.493.2377R. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 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. doi:10.1051/0004-6361:20042075. Bibcode: 2005A&A...436..253T. 
  9. ↑ 9.0 9.1 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. doi:10.1111/j.1365-2966.2010.16575.x. Bibcode: 2010MNRAS.405.1907B. 
  10. ↑ "Del Eri". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=Del+Eri. 
  11. ↑ Atlas Coeli Skalnaté Pleso II - Katalog 1950.0. Přírodovědecké Vydavatelstrí. 1951. p. 277. https://books.google.com/books?id=nXPvAAAAMAAJ&q=Rana. Retrieved 27 May 2019. 
  12. ↑ "Rana". IAU Working Group on Star Names. https://xing.fmi.uni-jena.de/mediawiki/index.php/Rana. 
  13. ↑ "Naming Stars". https://www.iau.org/public/themes/naming_stars/. 
  14. ↑ (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.
  15. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ↑ Kholopov, P. N.; Samus', N. N.; Kazarovets, E. V.; Kireeva, N. N. (1987). "The 68th Name-List of Variable Stars". Information Bulletin on Variable Stars 3058: 1. Bibcode: 1987IBVS.3058....1K. 
  17. ↑ Samus', N. N et al. (2017). "General catalogue of variable stars". Astronomy Reports. GCVS 5.1 61 (1): 80. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  18. ↑ 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. 
  19. ↑ 19.0 19.1 Laliotis, Katherine; Burt, Jennifer A.; Mamajek, Eric E.; Li, Zhexing; Perdelwitz, Volker; Zhao, Jinglin; Butler, R. Paul; Holden, Bradford et al. (2023-04-01). "Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions*". The Astronomical Journal 165 (4): 176. doi:10.3847/1538-3881/acc067. ISSN 0004-6256. Bibcode: 2023AJ....165..176L. 



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