Delta Ophiuchi

Delta Ophiuchi (δ Ophiuchi, abbreviated Delta Oph, δ Oph), formally named Yed Prior /ˌjɛd ˈpraɪər/,[13][14] is a star in the constellation of Ophiuchus. It forms a naked-eye optical double with Epsilon Ophiuchi (named Yed Posterior[14]). The apparent visual magnitude is 2.75,[2] making this a third-magnitude star and the fourth-brightest in the constellation. Parallax measurements from the Hipparcos spacecraft yield a distance estimate of approximately 171 light-years (52 parsecs) from the Sun (Epsilon Ophiuchi is approximately 108 light-years (33 parsecs)).[1]

δ Ophiuchi
Location of δ Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 16h 14m 20.73853s[1]
Declination –03° 41′ 39.5612″[1]
Apparent magnitude (V) 2.75[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M0.5 III[4]
U−B color index +1.96[2]
B−V color index +1.59[2]
Variable type Suspected[5]
Astrometry
Radial velocity (Rv)–19.9[6] km/s
Proper motion (μ) RA: –47.54[1] mas/yr
Dec.: –142.73[1] mas/yr
Parallax (π)19.06 ± 0.16 mas[1]
Distance171 ± 1 ly
(52.5 ± 0.4 pc)
Absolute magnitude (MV)–0.90[7]
Details
Mass1.5[8] M☉
Radius59[9] R☉
Surface gravity (log g)1.4[10] cgs
Temperature3,679[10] K
Metallicity [Fe/H]0.32[10] dex
Rotational velocity (v sin i)7.0[11] km/s
Other designations
1 Oph, BD-03 3903, FK5 603, HD 146051, HIP 79593, HR 6056, SAO 141052.[12]
Database references
SIMBADdata

Nomenclature

δ Ophiuchi (Latinised to Delta Ophiuchi) is the star's Bayer designation.

It bore the traditional name Yed Prior. Yed derives from the Arabic يد yad "hand". Delta and Epsilon Ophiuchi comprise the left hand of Ophiuchus (the Serpent Bearer) that holds the head of the serpent (Serpens Caput). Delta is Yed Prior as it leads Epsilon across the sky. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalogue and standardize proper names for stars. The WGSN approved the name Yed Prior for this star on 5 October 2016 and it is now so included in the List of IAU-approved Star Names.[14]

Delta Ophiuchi was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, the "Southern Line" of al-Nasaqān the "Two Lines",[16] along with Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Epsilon Ophiuchi, Zeta Ophiuchi and Gamma Ophiuchi.[17]

In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven ancient states in China and which mark the right borderline of the enclosure, consisting of Delta Ophiuchi, Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Beta Serpentis, Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Epsilon Ophiuchi and Zeta Ophiuchi.[18] Consequently, the Chinese name for Delta Ophiuchi itself is 天市右垣九 (Tiān Shì Yòu Yuán jiǔ, English: the Ninth Star of Right Wall of Heavenly Market Enclosure), representing the state of Liang (梁) (or Leang).[19][20]

Properties

Delta Ophiuchi has a stellar classification of M0.5 III,[4] making this a red giant star that has undergone expansion of its outer envelope after exhausting the supply of hydrogen at its core. It is currently on the asymptotic giant branch.[3] The measured angular diameter of this star, after correction for limb darkening, is 10.47 ± 0.12 mas.[21] At the estimated distance of Delta Ophiuchi,[1] this yields a physical size of about 59 times the radius of the Sun.[9] In spite of its enlarged size, this star has only 1.5 times the mass of the Sun and hence a much lower density.[8] The effective temperature of the outer atmosphere of Delta Ophiuchi is a relatively cool 3,679 K,[10] which is what gives it the orange-red hue of an M-type star.[22]

It is listed as a suspected variable star that may change by 0.03 in visual magnitude.[5][12] It has a low projected rotational velocity of 7.0 km s−1, which gives a minimum value for the azimuthal velocity along the star's equator.[11] The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is more than double the abundance in the Sun's photosphere.[10]

The star has a high optical linear polarisation that increases from red to blue wavelengths and displays some variability, this has been ascribed to either an asymmetric distribution of dust grains in an envelope expelled from it, or the presence of photometric hot spots.[23]

References
  1. van Leeuwen, F. (November 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. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". Astronomical Journal. 104 (1): 275–313. Bibcode:1992AJ....104..275E. doi:10.1086/116239.
  4. Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333
  5. Percy, J. R.; Shepherd, C. W. (October 1992), "A Photometric Survey of Small-Amplitude Red Variables", Information Bulletin on Variable Stars, 3792: 1, Bibcode:1992IBVS.3792....1P
  6. Wilson, Ralph Elmer (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication, Washington: Carnegie Institution of Washington, Bibcode:1953GCRV..C......0W
  7. Schmidt-Kaler, T.; Oestreicher, M. O. (October 1998), "The luminosity index for M stars and the distance to the LMC", Astronomische Nachrichten, 319 (6): 375–386, Bibcode:1998AN....319..375S, doi:10.1002/asna.2123190606
  8. Tsuji, Takashi (May 2007), "Isotopic abundances of Carbon and Oxygen in Oxygen-rich giant stars", in Kupka, F.; Roxburgh, I.; Chan, K. (eds.), Convection in Astrophysics, Proceedings of IAU Symposium #239 held 21-25 August, 2006 in Prague, Czech Republic, vol. 239, pp. 307–310, arXiv:astro-ph/0610180, Bibcode:2007IAUS..239..307T, doi:10.1017/S1743921307000622, S2CID 119362842
  9. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
  10. Oinas, V. (October 1977), "Neutral-ion anomaly in cool stars", Astronomy and Astrophysics, 61 (1): 17–20, Bibcode:1977A&A....61...17O
  11. 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
  12. "del Oph -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2010-07-06
  13. 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.
  14. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  15. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  16. Kunitzsch, P.; Smart, T. (2006), A Dictionary of Modern Star names: A Short Guide to 254 Star names and Their Derivations (Second Revised ed.), Cambridge, MA: Sky Publishing, p. 31, ISBN 1-931559-44-9
  17. Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 243, ISBN 0-486-21079-0, retrieved 2010-12-12
  18. (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.
  19. (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.
  20. (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived August 10, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  21. Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039
  22. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
  23. Cotton, D. V.; et al. (January 2016). "The linear polarization of Southern bright stars measured at the parts-per-million level". Monthly Notices of the Royal Astronomical Society. 455 (2): 1607–1628. arXiv:1509.07221. Bibcode:2016MNRAS.455.1607C. doi:10.1093/mnras/stv2185. S2CID 11191040.
  • Kaler, James B., "Yed Prior", Stars, University of Illinois, retrieved 2012-02-07
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