Astronomy:Iota Hydrae

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Short description: Star in the constellation Hydra
Iota Hydrae
Location of Iota Hydrae (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hydra
Right ascension  09h 39m 51.36145s[1]
Declination −01° 08′ 34.1135″[1]
Apparent magnitude (V) 3.91[2]
Characteristics
Spectral type K2.5 III[2]
B−V color index 1.32
Variable type Suspected[3]
Astrometry
Radial velocity (Rv)+24.19±0.36[4] km/s
Proper motion (μ) RA: +46.96[1] mas/yr
Dec.: −62.39[1] mas/yr
Parallax (π)12.39 ± 0.14[1] mas
Distance263 ± 3 ly
(80.7 ± 0.9 pc)
Absolute magnitude (MV)−0.63[5]
Details
Mass1.92[2] M☉
Radius30±0.04[6] R☉
Luminosity241±7[7] L☉
Surface gravity (log g)1.78±0.04[7] cgs
Temperature4,238±22[7] K
Metallicity [Fe/H]−0.06±0.05[7] dex
Rotational velocity (v sin i)4.5[4] km/s
Age2.47[2] Gyr
Other designations
Ukdah, ι Hya, 35 Hydrae, BD−00°2231, FK5 1250, HD 83618, HIP 47431, HR 3845, SAO 137035.[8]
Database references
SIMBADdata

Iota Hydrae (ι Hydrae, abbreviated Iota Hya, ι Hya), formally named Ukdah /ˈʌkdə/,[9] is a star in the constellation of Hydra, about 8° to the north-northwest of Alphard (Alpha Hydrae)[10] and just to the south of the celestial equator.[11] Visible to the naked eye, it is a suspected variable star with an apparent visual magnitude that ranges between 3.87 and 3.91.[3] Based upon an annual parallax shift of 12.39 mas measured during the Hipparcos mission,[1] it is located around 263 light-years distant.

Nomenclature

ι Hydrae (Latinised to Iota Hydrae) is the star's Bayer designation.

This star along with Tau1 Hydrae, Tau2 Hydrae and 33 Hydrae (A Hydrae), were Ptolemy's Καμπή (Kampē); but Kazwini knew them as عقدة ʽuqdah (or ʽuḳdah) "knot".[12] According to a 1971 NASA memorandum,[13] Ukdah was the name of an asterism of four stars: Tau1 Hydrae as Uḳdah I, Tau2 Hydrae as Uḳdah II, 33 Hydrae as Uḳdah III and Iota Hydrae as Uḳdah IV. In 2016, the IAU organized a Working Group on Star Names (WGSN)[14] to catalog and standardize proper names for stars. The WGSN approved the name Ukdah for Iota Hydrae on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.[9]

In Chinese, 星宿 (Xīng Sù), meaning Star or asterism, refers to an asterism consisting of ι Hydrae, Alphard, τ1 Hydrae, τ2 Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428.[15] Consequently, ι Hydrae are known as 星宿四 (Xīng Sù sì, English: the Fourth Star of Star).[16]

Properties

This is an evolved K-type giant star with a stellar classification of K2.5 III.[2] It is a Barium star, which means that, for a giant star, it displays unusually strong absorption lines of singly-ionized barium and strontium.[17] Iota Hydrae has nearly twice the mass of the Sun[2] and has expanded to 30 times the Sun's radius.[6] It is around 2.5 billion years old[2] and is spinning with a leisurely projected rotational velocity of 4.5 km/s.[4] It may be a member of the Wolf 630 moving group of stars that share a common trajectory through space.[18]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal 150 (3): 23, doi:10.1088/0004-6256/150/3/88, 88, Bibcode: 2015AJ....150...88L. 
  3. ↑ 3.0 3.1 Samus, N. N. et al. (2009), "General Catalogue of Variable Stars", VizieR On-line Data Catalog 1, Bibcode: 2009yCat....102025S. 
  4. ↑ 4.0 4.1 4.2 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, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M. 
  5. ↑ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  6. ↑ 6.0 6.1 Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Zavala, R. T.; Benson, James A.; Hutter, Donald J.; Tycner, Christopher; Van Belle, Gerard T. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal 155 (1): 30, doi:10.3847/1538-3881/aa9d8b, Bibcode: 2018AJ....155...30B. 
  7. ↑ 7.0 7.1 7.2 7.3 Soubiran, C.; Creevey, O. L.; Lagarde, N.; Brouillet, N.; Jofré, P.; Casamiquela, L.; Heiter, U.; Aguilera-Gómez, C. et al. (February 2024), Gaia FGK benchmark stars: Fundamental Teff and log g of the third version, 682, pp. 23, doi:10.1051/0004-6361/202347136, Bibcode: 2024A&A...682A.145S 
  8. ↑ "iot Hya". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=iot+Hya. 
  9. ↑ 9.0 9.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  10. ↑ O'Meara, Steve (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 84, ISBN 978-0521858939, https://books.google.com/books?id=Nyh9fAC_tpIC&pg=PA84. 
  11. ↑ Moore, Patrick (2013), The Observer's Year: 366 Nights of the Universe, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 71, ISBN 978-1447136132, https://books.google.com/books?id=p87TBwAAQBAJ&pg=PA71-IA11. 
  12. ↑ Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 250. ISBN 0-486-21079-0. https://archive.org/details/starnamestheirlo00alle/page/250. Retrieved 2010-12-12. 
  13. ↑ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  14. ↑ "IAU Working Group on Star Names (WGSN)". https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  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) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 29 日
  17. ↑ Lu, Phillip K. (June 1991), "Taxonomy of barium stars", Astronomical Journal 101: 2229–2254, doi:10.1086/115845, Bibcode: 1991AJ....101.2229L. 
  18. ↑ McDonald, A. R. E.; Hearnshaw, J. B. (August 1983), "The Wolf 630 moving group of stars", Monthly Notices of the Royal Astronomical Society 204 (3): 841–852, doi:10.1093/mnras/204.3.841, Bibcode: 1983MNRAS.204..841M. 



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