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U Aquarii

The visual band light curve of U Aquarii, from AAVSO data
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Aquarius
Right ascension	22 03 19.69905
Declination	−16° 37′ 35.2811″
Apparent magnitude (V)	10.6 to 15.9
Characteristics
Spectral type	C-Hd
U−B color index	0.07
B−V color index	0.66
Variable type	R CrB
Astrometry
Radial velocity (Rv)	+89.49±1.54 km/s
Proper motion (μ)	RA: 2.780 mas/yr Dec.: −1.907 mas/yr
Parallax (π)	0.0859 ± 0.0222 mas
Distance	approx. 38,000 ly (approx. 12,000 pc)
Details
Mass	4.5 M☉
Surface gravity (log g)	2.28 cgs
Temperature	5,500 K
Metallicity	−0.99 dex
Rotational velocity (v sin i)	8.4 km/s
Other designations
U Aqr, BD−17°6424, HIP 108876, IRAS 22006-1652
Database references
SIMBAD	data

U Aquarii, abbreviated U Aqr, is a variable star in the equatorial constellation of Aquarius. It is invisible to the naked eye, having an apparent visual magnitude that ranges from 10.6 down to as low as 15.9. Based on parallax measurements, the distance to this star is approximately 38 kly (12 kpc). In 1990, W. A. Lawson and associates provided a distance estimate of 43 kly (13.2 kpc) based on the assumption of a bolometric magnitude of −5. It appears to lie several kiloparsecs below the galactic plane, and thus may belong to an old stellar population.

Christian Heinrich Friedrich Peters discovered that U Aquarii is a variable star based on observations made from 1875 to 1878. Its variable star designation was published in Annie Jump Cannon's Second catalogue of variable stars in 1907, at which time the class of variable star it belonged to was still unknown.

The stellar classification of this star is C-Hd, and it is classified as a R Coronae Borealis variable. It is a carbon star with a hydrogen-deficient spectra that also shows evidence of s-process elements, including overabundances of strontium and yttrium, but no barium. This combination of properties is exceptionally rare; only one other example has been found as of 2012. The elemental abundances are explained as the result of a single neutron exposure event, which is difficult to reconcile with a conjecture that this may be a post-AGB-type star. In 1999, U Aqr was proposed to be a Thorne-Zytkow object, instead of being a simple R Coronae Borealis variable.

References

1. "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
2. ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
3. ^ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
4. ^ Bond, H. E.; et al. (October 1979). "The extraordinary composition of U Aquarii". Astrophysical Journal. 233: 205–210. Bibcode:1979ApJ...233..205B. doi:10.1086/157382.
5. ^ Lawson, W. A.; et al. (November 1990). "The photometric characteristics of cool hydrogen-deficient carbon stars". Monthly Notices of the Royal Astronomical Society. 247: 91. Bibcode:1990MNRAS.247...91L.
6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
7. ^ Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevič, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; De Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy and Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. S2CID 131780028.
8. Majewski, Steven R.; Schiavon, Ricardo P.; Frinchaboy, Peter M.; Allende Prieto, Carlos; Barkhouser, Robert; Bizyaev, Dmitry; Blank, Basil; Brunner, Sophia; Burton, Adam; Carrera, Ricardo; Chojnowski, S. Drew; Cunha, Kátia; Epstein, Courtney; Fitzgerald, Greg; García Pérez, Ana E.; Hearty, Fred R.; Henderson, Chuck; Holtzman, Jon A.; Johnson, Jennifer A.; Lam, Charles R.; Lawler, James E.; Maseman, Paul; Mészáros, Szabolcs; Nelson, Matthew; Nguyen, Duy Coung; Nidever, David L.; Pinsonneault, Marc; Shetrone, Matthew; Smee, Stephen; et al. (2017). "The Apache Point Observatory Galactic Evolution Experiment (APOGEE)". The Astronomical Journal. 154 (3): 94. arXiv:1509.05420. Bibcode:2017AJ....154...94M. doi:10.3847/1538-3881/aa784d. S2CID 119293367.
9. "U Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-01.
10. ^ Cannon, Annie J. (1907). "Second catalogue of variable stars". Annals of Harvard College Observatory. 55: 1–94. Bibcode:1907AnHar..55....1C. Retrieved 20 November 2024.
11. "U Aqr". The International Variable Star Index. AAVSO. Retrieved 20 November 2024.
12. ^ Malaney, R. A. (October 1985). "On the nature of the neutron exposure event of U Aquarii". Monthly Notices of the Royal Astronomical Society. 216 (3): 743–752. Bibcode:1985MNRAS.216..743M. doi:10.1093/mnras/216.3.743.
13. Goswami, Aruna (2012). Prugniel, Philippe; Singh, Harinder P. (eds.). Spectroscopic characterization of FHLC stars from the Hamburg/ESO survey and a newly found HdC star. International Workshop on Stellar Libraries, Proceedings of a conference held 5-9 December, 2011 at University of Delhi, India. Astronomical Society of India Conference Series. Vol. 6. p. 189. arXiv:1204.1806. Bibcode:2012ASInC...6..189G. ISBN 978-81-922926-4-9.
14. Vanture, Andrew D.; et al. (April 1, 1999). "Is U Aquarii a Thorne-Żytkow Object?". The Astrophysical Journal. 514 (2): 932–938. Bibcode:1999ApJ...514..932V. doi:10.1086/306956.

v t e Constellation of Aquarius
Aquarius in Chinese astronomy Aquarius Stream List of stars in Aquarius
Stars	Bayer α (Sadalmelik) β (Sadalsuud) γ (Sadachbia) δ (Skat) ε (Albali) ζ η θ (Ancha) ι κ (Situla) λ (Hydor) μ ν ξ (Bunda) ο π ρ σ τ τ υ φ χ ψ (91) ψ ψ ω ω A A b b b c c c d e f g g h i i i k α PsA C Flamsteed 1 4 5 7 8 9 10 11 12 14 15 16 17 18 19 20 21 24 26 28 29 30 32 35 36 37 39 40 41 42 44 45 47 49 50 51 54 56 58 60 61 64 65 67 70 72 74 75 77 78 81 82 84 85 87 94 96 97 100 Variable R U AE DV EP EW EZ FO HK IL HU IZ LL LP HR 8017 8056 8121 8263 8363 8453 8500 8507 8581 8612 8629 8645 8716 8783 8836 8856 8879 8924 9014 HD 206610 (Bosona) 210277 212771 (Lionrock) 215152 219617 220466 220689 222093 222582 Other 2MASS J21392676+0220226 BD−22 5866 Gliese 849 K2-21 K2-28 K2-58 K2-72 K2-138 LS IV-14 116 Sneden's Star TRAPPIST-1 WASP-6 (Márohu) WASP-47 WASP-69 WASP-75
Exoplanets ψ Aquarii b Gliese 849 b Gliese 876 b c d e HD 206610 b HD 210277 b HD 212771 b (Victoriapeak) HD 221416 b HD 222582 b K2-66b K2-72b c d e K2-138b TRAPPIST-1b c d e f g h WASP-6b
Star clusters Messier 2 Messier 72 Messier 73
Nebulae Helix Nebula Saturn Nebula
Galaxies	NGC 6975 7001 7010 7047 7051 7065 7069 7077 7081 7184 7222 7252 7257 7301 7302 7393 7492 7585 7592 7600 7606 7723 7727 7759 Other Aquarius Dwarf ESO 603-G21 Lyman-alpha blob 1 PGC 1228197 PHL 293B SMM J2135-0102 WISE J224607.57−052635.0 J2345-0449
Galaxy clusters Abell 2597 RXC J2211.7-0350 XMMXCS 2215-1738
Astronomical events SN 2213-1745
Category

• Carbon stars
• R Coronae Borealis variables
• Aquarius (constellation)
• Durchmusterung objects
• Hipparcos objects
• Objects with variable star designations