99 Aquarii
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Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Aquarius |
Right ascension | 23h 26m 02.78566s[1] |
Declination | –20° 38′ 31.251″[1] |
Apparent magnitude (V) | 4.37[2] |
Characteristics | |
Spectral type | K4 III[3] |
U−B color index | +1.815[2] |
B−V color index | +1.431[2] |
Variable type | Suspected[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[1] mas |
Distance | 283 ± 5 ly (87 ± 2 pc) |
Details | |
Radius | 33[6] R☉ |
Surface gravity (log g) | 1.66[7] cgs |
Temperature | 3980[7] K |
Metallicity [Fe/H] | –0.20[7] dex |
Other designations | |
99 Aquarii is the Flamsteed designation for a star in the equatorial constellation of Aquarius. The Bayer designation for this star is b2 Aquarii. It is visible to the naked eye with an apparent visual magnitude of 4.37;[2] according to the Bortle Dark-Sky Scale this is bright enough to be seen even from city skies under ideal viewing conditions. Based upon parallax measurements, the distance to this star is around 283 light-years (87 parsecs).[1]
This is a giant star with a stellar classification of K4 III.[3] It is a suspected variable star that apparently ranges in magnitude between 4.35 and 4.45.[4] The measured angular diameter of this star is 3.55 ± 0.21 mas.[9] At the estimated distance of Delta Ophiuchi,[1] this yields a physical size of about 33 times the radius of the Sun.[6] The outer atmosphere has an effective 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 the Ursa Major Moving Group based on the work of American astronomer Nancy Roman, but this membership is now in question.[11]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 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.
- ↑ 2.0 2.1 2.2 2.3 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.
- ↑ 3.0 3.1 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.
- ↑ 4.0 4.1 Samus, N. N. et al. (March 2012), "NSV 14554", General Catalog of Variable Stars, retrieved 2012-07-12.
- ↑ Wilson, Ralph Elmer (1953), General Catalogue of Stellar Radial Velocities, Washington: Carnegie Institution of Washington, Bibcode:1953QB901.W495......
- ↑ 6.0 6.1 Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library 1 (3 ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R*) is given by:
- ↑ 7.0 7.1 7.2 7.3 McWilliam, 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.
- ↑ "99 Aqr -- Variable Star", SIMBAD Astronomical Object Database (Centre de Données astronomiques de Strasbourg), retrieved 2012-07-11.
- ↑ 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.
- ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16.
- ↑ 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.
External links
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