98 Aquarii

98 Aquarii
Diagram showing star positions and boundaries of the Aquarius constellation and its surroundings


Location of 98 Aquarii (circled)

Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 23h 22m 58.22606s[1]
Declination –20° 06′ 02.0963″[1]
Apparent magnitude (V) +3.97[2]
Characteristics
Spectral type K0 III[3]
U−B color index +0.948[2]
B−V color index +1.089[2]
Astrometry
Radial velocity (Rv)–6.5[4] km/s
Proper motion (μ) RA: –121.28[1] mas/yr
Dec.: –97.59[1] mas/yr
Parallax (π)19.96 ± 0.23[1] mas
Distance163 ± 2 ly
(50.1 ± 0.6 pc)
Details
Mass2.1[5] M☉
Radius14[6] R☉
Surface gravity (log g)2.4[5] cgs
Temperature4,630[5] K
Metallicity [Fe/H]–0.30[5] dex
Other designations
BD–20 6587, FK5 1612, HD 220321, HIP 115438, HR 8892, SAO 191858.[7]

98 Aquarii (abbreviated 98 Aqr) is a star in the equatorial constellation of Aquarius. 98 Aquarii is the Flamsteed designation although it also bears the Bayer designation b1 Aquarii. It is visible to the naked eye with an apparent visual magnitude of +3.97.[2] The distance to this star, 163 light-years (50 parsecs), is known from parallax measurements made with the Hipparcos spacecraft.[1]

With over double the mass of the Sun,[5] this is an evolved giant star that has a stellar classification of K0 III.[3] The measured angular diameter of this star is 2.54 ± 0.13 mas.[8] At the estimated distance of 98 Aquarii,[1] this yields a physical size of about 14 times the radius of the Sun.[6] The expanded outer envelope has an effective temperature of 4,630 K,[5] giving it the orange glow of a K-type star.[9]

References

  1. 1 2 3 4 5 6 7 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.
  2. 1 2 3 4 Jennens, 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: 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
  3. 1 2 Houk, Nancy (1978), Michigan catalogue of two-dimensional spectral types for the HD stars 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  4. ↑ Wielen, R.; et al. (1999), Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions (35), Astronomisches Rechen-Institut Heidelberg, Bibcode:1999VeARI..35....1W.
  5. 1 2 3 4 5 6 Melo, C. H. F.; et al. (August 2005), "On the nature of lithium-rich giant stars. Constraints from beryllium abundances", Astronomy and Astrophysics 439 (1): 227–235, arXiv:astro-ph/0504133, Bibcode:2005A&A...439..227M, doi:10.1051/0004-6361:20041805.
  6. 1 2 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R*) is given by:
    \begin{align} 2\cdot R_* & = \frac{(50.1\cdot 2.54\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\ & \approx 27.4\cdot R_{\bigodot} \end{align}
  7. ↑ "98 Aqr -- Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2006-11-05.
  8. ↑ Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics 431: 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
  9. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16.
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