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99 Aquarii

From Wikipedia, the free encyclopedia
Orange-hued giant star in the constellation Aquarius
This article is about b2 Aquarii. For other star systems with thisBayer designation, seeb Aquarii.
99 Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings
Location of 99 Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
ConstellationAquarius
Right ascension23h 26m 02.78566s[1]
Declination–20° 38′ 31.251″[1]
Apparent magnitude (V)4.37[2]
Characteristics
Spectral typeK4 III[3]
U−Bcolor index+1.815[2]
B−Vcolor index+1.431[2]
Variable typeSuspected[4]
Astrometry
Radial velocity (Rv)+15.7[5] km/s
Proper motion (μ)RA: –50.72[1]mas/yr
Dec.: –64.22[1]mas/yr
Parallax (π)11.51±0.21 mas[1]
Distance283 ± 5 ly
(87 ± 2 pc)
Details
Radius33[6] R☉
Surface gravity (log g)1.66[7] cgs
Temperature3980[7] K
Metallicity [Fe/H]–0.20[7] dex
Other designations
BD–21 6420,HD 220704,HIP 115669,HR 8906,NSV 14554,SAO 191900.[8]
Database references
SIMBADdata

99 Aquarii (abbreviated99 Aqr) is astar in theequatorialconstellation ofAquarius.99 Aquarii is theFlamsteed designation, although it also bears theBayer designationb2 Aquarii. It is visible to the naked eye with anapparent visual magnitude of 4.38;[2] according to theBortle Dark-Sky Scale this is bright enough to be seen even from city skies under ideal viewing conditions. Based uponparallax measurements, the distance to this star is around 283light-years (87parsecs).[1]

This is agiant star with astellar classification of K4 III.[3] It is a suspectedvariable star that apparently ranges in magnitude between 4.35 and 4.45.[4] The measuredangular diameter of this star is3.55 ± 0.21mas.[9] At the estimated distance of Delta Ophiuchi,[1] this yields a physical size of about 33 times theradius of the Sun.[6] Theouter atmosphere has aneffective temperature of 3980 K,[7] giving it the orange-hued glow of a cool,K-type star.[10]

This star was a candidate member of theUrsa Major Moving Group based on the work of American astronomerNancy Roman, but this membership is now in question.[11]

References

[edit]
  1. ^abcdefgvan 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. ^abcdJennens, P. A.; Helfer, H. L. (September 1975), "A new photometric metal abundance and luminosity calibration for field G and K giants.",Monthly Notices of the Royal Astronomical Society,172 (3):667–679,Bibcode:1975MNRAS.172..667J,doi:10.1093/mnras/172.3.667.
  3. ^abHouk, Nancy (1978),Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan,Bibcode:1988mcts.book.....H.
  4. ^abSamus, N. N.; et al. (March 2012),"NSV 14554",General Catalog of Variable Stars, retrieved2012-07-12.
  5. ^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.
  6. ^abLang, 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:
    2⋅R∗=(87⋅3.55⋅10−3) AU0.0046491 AU/R⨀≈66⋅R⨀{\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(87\cdot 3.55\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 66\cdot R_{\bigodot }\end{aligned}}}
  7. ^abcdMcWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances",Astrophysical Journal Supplement Series,74:1075–1128,Bibcode:1990ApJS...74.1075M,doi:10.1086/191527.
  8. ^"* 99 Aqr".SIMBAD.Centre de données astronomiques de Strasbourg. Retrieved2012-07-11.
  9. ^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.
  10. ^"The Colour of Stars",Australia Telescope, Outreach and Education,Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived fromthe original on March 18, 2012, retrieved2012-01-16.
  11. ^Chupina, N. V.; Reva, V. G.; Vereshchagin, S. V. (June 2006), "Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars",Astronomy and Astrophysics,451 (3):909–916,Bibcode:2006A&A...451..909C,doi:10.1051/0004-6361:20054009. See table 7.

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