98 Aquarii

98 Aquarii
	Location of 98 Aquarii (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Aquarius
Right ascension	23h 22m 58.22606s
Declination	–20° 06′ 02.0963″
Apparent magnitude (V)	+3.97
Characteristics
Spectral type	K0 III
U−B color index	+0.948
B−V color index	+1.089
Astrometry
Radial velocity (Rv)	–6.5 km/s
Proper motion (μ)	RA: –121.28 mas/yr ; Dec.: –97.59 mas/yr
Parallax (π)	19.96 ± 0.23 mas
Distance	163 ± 2 ly ; (50.1 ± 0.6 pc)
Details
Mass	2.1 M☉
Radius	14 R☉
Surface gravity (log g)	2.4 cgs
Temperature	4,630 K
Metallicity [Fe/H]	–0.30 dex
Other designations
	BD–20 6587, FK5 1612, HD 220321, HIP 115438, HR 8892, SAO 191858.
Database references
SIMBAD	data

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

^ ^a ^b ^c ^d ^e ^f ^g 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.
^ ^a ^b ^c ^d 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 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.
^ ^a ^b Houk, 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
^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
^ ^a ^b ^c ^d ^e ^f 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, S2CID 10580797.
^ ^a ^b 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:
${\begin{aligned}2\cdot R_{*}&={\frac {(50.1\cdot 2.54\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 27.4\cdot R_{\bigodot }\end{aligned}}$
^ "* 98 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-05.
^ 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.
^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16.

[aaa474_2_653-1] ^ ^a ^b ^c ^d ^e ^f ^g 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.

[mnras172_667-2] 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 (3): 667–679, Bibcode:1975MNRAS.172..667J, doi:10.1093/mnras/172.3.667.

[houk1978-3] Houk, 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

[scfs-4] Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.

[aaa439_1_227-5] ^ ^a ^b ^c ^d ^e ^f 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, S2CID 10580797.

[lang2006-6] 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:
${\begin{aligned}2\cdot R_{*}&={\frac {(50.1\cdot 2.54\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 27.4\cdot R_{\bigodot }\end{aligned}}$

[SIMBAD-7] "* 98 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-11-05.

[aaa431_773-8] 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.

[csiro-9] "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16.

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98 Aquarii

References

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