U Aquarii: Difference between revisions
Praemonitus (talk | contribs) Update description and add refs. |
Mark viking (talk | contribs) Adding local short description: "Star in the constellation of Aquarius", overriding Wikidata description "star" (Shortdesc helper) |
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Revision as of 20:21, 2 January 2021
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 03m 19.69915s[1] |
| Declination | −16° 37′ 35.2804″[1] |
| Apparent magnitude (V) | 10.6 to 15.9[2] |
| Characteristics | |
| Spectral type | C-Hd[3] |
| U−B color index | 0.07[4] |
| B−V color index | 0.66[4] |
| Variable type | R CrB[2] |
| Astrometry | |
| Radial velocity (Rv) | +89.49±1.54[1] km/s |
| Proper motion (μ) | RA: 2.688[1] mas/yr Dec.: −1.930[1] mas/yr |
| Parallax (π) | 0.1906 ± 0.0660 mas[1] |
| Distance | approx. 17,000 ly (approx. 5,000 pc) |
| Details | |
| Temperature | 5,500[4] K |
| Other designations | |
| 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.[2] Based on parallax measurements, the distance to this star is approximately 17.1 kly (5.25 kpc). In 1990, W. A. Lawson and associates provided a much larger distance estimate of 43 kly (13.2 kpc).[4] It appears to lie several kiloparsecs below the galactic plane, and thus may belong to an old stellar population.[3]
The stellar classification of this star is C-Hd,[3] and it is classified as a R Coronae Borealis variable.[2] It is a carbon star with a hydrogen-deficient spectra that also shows evidence of s-process elements,[3] including overabundances of strontium and yttrium, but no barium.[6] This combination of properties is exceptionally rare; only one other example has been found as of 2012.[7] 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.[6] In 1999, U Aqr was proposed to be a Thorne-Zytkow object, instead of being a simple R Coronae Borealis variable.[8]
References
- ^ a b c d e f 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.
- ^ a b c d 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.
- ^ a b c d 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.
- ^ a b c d 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.
- ^ "U Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-01-01.
- ^ a b Malaney, R. A. (October 1985). "On the nature of the neutron exposure event of U Aquarii". Monthly Notices of the Royal Astronomical Society. 216: 743–752. Bibcode:1985MNRAS.216..743M. doi:10.1093/mnras/216.3.743.
- ^ Goswami, Aruna (2012). Prugniel, Philippe; Singh, Harinder P. (eds.). "Spectroscopic charaterization of FHLC stars from the Hamburg/ESO survey and a newly found HdC star". Astronomical Society of India Conference Series. 6: 189. arXiv:1204.1806. Bibcode:2012ASInC...6..189G. ISBN 978-81-922926-4-9.
{{cite journal}}: Cite journal requires|journal=(help); Unknown parameter|conference=ignored (help) - ^ 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.
