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{{distinguish|Upsilon Aquarii}}
{{Orphan|date=July 2011}}
{{short description|Star in the constellation of Aquarius}}

{{Starbox begin
{{Starbox begin}}
{{Starbox image
| name = [[Variable star designation|U Aquarii]]}}
| image = [[Image:UAqrLightCurve.png|250px]]
| caption = The [[Photometric_system#Photometric_letters|visual band]] [[light curve]] of U Aquarii, from AAVSO data<ref name="aavso"/>
}}
{{Starbox observe
{{Starbox observe
| epoch = [[J2000.0]]
| epoch = [[J2000.0]]
| equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
| equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
| constell = [[Aquarius (constellation)|Aquarius]]
| constell = [[Aquarius (constellation)|Aquarius]]
| ra = {{RA|22|03|19.69905}}<ref name=edr3/>
| ra = {{RA|22|03|19.6992}}<ref name=sb0>{{SIMBAD link|U+Aqr|V* U Aqr -- Variable Star of R CrB type}}, database entry, [[SIMBAD]]. Accessed on line November 10, 2009.</ref>
| dec = {{DEC|−16|37|35.288}}<ref name=sb0 />
| dec = {{DEC|−16|37|35.2811}}<ref name=edr3/>
| appmag_v = 10.6&nbsp;to&nbsp;15.9<ref name=Samus_et_al_2017/>
| appmag_v=10.6&nbsp;to&nbsp;15.9<ref name=gcvs1>U Aqr, database entry, [http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/iii.dat The combined table of GCVS Vols I-III and NL 67-78 with improved coordinates, General Catalogue of Variable Stars], Sternberg Astronomical Institute, Moscow, Russia. Accessed on line November 10, 2009.</ref>
}}
}}
{{Starbox character
{{Starbox character
| b-v = 1.0<ref name=sb0 />
| type =
| v-r = 0.4<ref name=sb0 />
| class = C-Hd<ref name=Bond_et_al_1979/>
| variable = [[R Coronae Borealis variable|RCB]]<ref name=gcvs1 />
| b-v = 0.66<ref name=Lawson_et_al_1990/>
| u-b = 0.07<ref name=Lawson_et_al_1990/>
| variable = [[R Coronae Borealis variable|R CrB]]<ref name=Samus_et_al_2017/>
}}
}}
{{Starbox astrometry
{{Starbox astrometry
| prop_mo_ra = 3.03<ref name=sb0 />
| radial_v = {{val|+89.49|1.54}}<ref name=GaiaDR2/>
| prop_mo_dec = −2.53<ref name=sb0 />
| prop_mo_ra = 2.780<ref name=edr3/>
| prop_mo_dec = −1.907<ref name=edr3/>
| parallax = 3.58
| p_error = 2.55
| parallax = 0.0859
| p_error = 0.0222
| parallax_footnote = <ref name=sb0 />
| parallax_footnote = <ref name=edr3/>
| absmag_v= 6<ref>From apparent magnitude and parallax.</ref>
| absmag_v =
}}
{{Starbox detail
| source =
| mass = 4.5<ref name=starhorse/>
| radius =
| gravity = 2.28<ref name=starhorse/>
| luminosity =
| temperature = 5,500<ref name=Lawson_et_al_1990/>
| metal_fe = −0.99<ref name=starhorse/>
| rotational_velocity = 8.4<ref name=majewski2017/>
| rotation =
| age_gyr =
}}
}}
{{Starbox catalog
{{Starbox catalog
| names=U&nbsp;Aqr, [[Durchmusterung|BD]]−17&nbsp;6424, [[Hipparcos Catalogue|HIP]]&nbsp;108876.<ref name=sb0 />}}
| names = {{odlist | V=U&nbsp;Aqr | BD=−17°6424 | HIP=108876 | IRAS=22006-1652 }}<ref name=SIMBAD/>
}}
{{Starbox reference
{{Starbox reference
| Simbad=U+Aqr}}
| Simbad = U+Aqr
}}
{{Starbox end}}
{{Starbox end}}


'''U&nbsp;Aquarii''' ('''U&nbsp;Aqr''') is a [[star]] in the [[constellation]] of [[Aquarius (constellation)|Aquarius]].<ref name=sb0 /> It has an [[apparent visual magnitude]] which varies between 10.6 and 15.9.<ref name=gcvs1 />
'''U&nbsp;Aquarii''', abbreviated '''U&nbsp;Aqr''', is a [[variable star]] in the [[celestial equator|equatorial]] [[constellation]] of [[Aquarius (constellation)|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.<ref name=Samus_et_al_2017 /> Based on [[stellar parallax|parallax]] measurements, the distance to this star is approximately {{convert|38|kly|kpc|abbr=on|lk=on}}. In 1990, W. A. Lawson and associates provided a distance estimate of {{convert|13.2|kpc|kly|order=flip|abbr=on|lk=off}} based on the assumption of a [[bolometric magnitude]] of −5.<ref name=Lawson_et_al_1990/> It appears to lie several kiloparsecs below the galactic plane, and thus may belong to an old stellar population.<ref name=Bond_et_al_1979/>

The [[stellar classification]] of this star is C-Hd,<ref name=Bond_et_al_1979/> and it is classified as a [[R Coronae Borealis variable]].<ref name=Samus_et_al_2017/> It is a [[carbon star]] with a [[Hydrogen-deficient star|hydrogen-deficient]] [[stellar spectrum|spectra]] that also shows evidence of [[s-process]] elements,<ref name=Bond_et_al_1979/> including overabundances of strontium and yttrium, but no barium.<ref name=Malaney1985/> This combination of properties is exceptionally rare; only one other example has been found as of 2012.<ref name=Goswami2012/> 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-[[Asymptotic giant branch|AGB]]-type star.<ref name=Malaney1985/> In 1999, U Aqr was proposed to be a [[Thorne-Zytkow object]], instead of being a simple R Coronae Borealis variable.<ref name=Vanture_et_al_1999/>


==References==
==References==
{{reflist}}
{{reflist|refs=


<ref name="aavso">{{cite web |title=Download Data |url=https://www.aavso.org/data-download |website=aavso.org |publisher=AAVSO |access-date=1 October 2021}}</ref>
[[Category:Aquarius constellation]]
[[Category:Unclassified stars]]
[[Category:HIP objects|108876]]
[[Category:R Coronae Borealis variables]]
[[Category:Objects named with variable star designations|Aquarii, U]]


<ref name=SIMBAD>{{cite simbad
[[fa:یو دلو]]
| title=U Aqr | access-date=2021-01-01 }}</ref>
[[pl:U Aquarii]]

<ref name=GaiaDR2>{{Cite Gaia DR2|6826788566384202496}}</ref>

<ref name=edr3>{{cite Gaia EDR3|6826788566384202496}}</ref>

<ref name=Goswami2012>{{cite conference
| title=Spectroscopic characterization of FHLC stars from the Hamburg/ESO survey and a newly found HdC star
| last=Goswami | first=Aruna
| conference=International Workshop on Stellar Libraries, Proceedings of a conference held 5-9 December, 2011 at University of Delhi, India
| editor1-first=Philippe | editor1-last=Prugniel
| editor2-first=Harinder P. | editor2-last=Singh
| series=Astronomical Society of India Conference Series
| volume=6 | date=2012 | page=189 | isbn=978-81-922926-4-9
| arxiv=1204.1806 | bibcode=2012ASInC...6..189G }}</ref>

<ref name=Malaney1985>{{cite journal
| title=On the nature of the neutron exposure event of U Aquarii
| last=Malaney | first=R. A.
| journal=Monthly Notices of the Royal Astronomical Society
| volume=216 | pages=743–752 | date=October 1985
| issue=3 | bibcode=1985MNRAS.216..743M | doi=10.1093/mnras/216.3.743 | doi-access=free }}</ref>

<ref name=Bond_et_al_1979>{{cite journal
| title=The extraordinary composition of U Aquarii
| display-authors=1 | last1=Bond | first1=H. E.
| last2=Luck | first2=R. E. | last3=Newman | first3=M. J.
| journal=Astrophysical Journal
| volume=233 | pages=205–210 | date=October 1979
| bibcode=1979ApJ...233..205B | doi=10.1086/157382 | doi-access=free }}</ref>

<ref name=Lawson_et_al_1990>{{cite journal
| title=The photometric characteristics of cool hydrogen-deficient carbon stars.
| last1=Lawson | first1=W. A. | last2=Cottrelll | first2=P. L.
| last3=Kilmartin | first3=P. M. | last4=Gilmore | first4=A. C.
| display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society
| volume=247 | page=91 | date=November 1990
| bibcode=1990MNRAS.247...91L }}</ref>

<ref name=Samus_et_al_2017>{{cite journal
| title=General catalogue of variable stars: Version GCVS 5.1
| last1=Samus' | first1=N. N | last2=Kazarovets | first2=E. V
| last3=Durlevich | first3=O. V | last4=Kireeva | first4=N. N
| last5=Pastukhova | first5=E. N | journal=Astronomy Reports
| volume=61 | issue=1 | pages=80 | year=2017
| bibcode=2017ARep...61...80S | s2cid=125853869
| doi=10.1134/S1063772917010085 }}</ref>

<ref name=Vanture_et_al_1999>{{cite journal
| title= Is U Aquarii a Thorne-Żytkow Object?
| display-authors=1 | first1=Andrew D. | last1=Vanture
| first2=Daniel | last2=Zucker | first3=George | last3=Wallerstein
| journal=The Astrophysical Journal
| date=April 1, 1999 | volume=514 | number=2 | pages=932–938
| bibcode=1999ApJ...514..932V | doi=10.1086/306956 | doi-access=free }}</ref>

<ref name=majewski2017>{{cite journal |bibcode=2017AJ....154...94M |title=The Apache Point Observatory Galactic Evolution Experiment (APOGEE) |last1=Majewski |first1=Steven R. |last2=Schiavon |first2=Ricardo P. |last3=Frinchaboy |first3=Peter M. |last4=Allende Prieto |first4=Carlos |last5=Barkhouser |first5=Robert |last6=Bizyaev |first6=Dmitry |last7=Blank |first7=Basil |last8=Brunner |first8=Sophia |last9=Burton |first9=Adam |last10=Carrera |first10=Ricardo |last11=Chojnowski |first11=S. Drew |last12=Cunha |first12=Kátia |last13=Epstein |first13=Courtney |last14=Fitzgerald |first14=Greg |last15=García Pérez |first15=Ana E. |last16=Hearty |first16=Fred R. |last17=Henderson |first17=Chuck |last18=Holtzman |first18=Jon A. |last19=Johnson |first19=Jennifer A. |last20=Lam |first20=Charles R. |last21=Lawler |first21=James E. |last22=Maseman |first22=Paul |last23=Mészáros |first23=Szabolcs |last24=Nelson |first24=Matthew |last25=Nguyen |first25=Duy Coung |last26=Nidever |first26=David L. |last27=Pinsonneault |first27=Marc |last28=Shetrone |first28=Matthew |last29=Smee |first29=Stephen |last30=Smith |first30=Verne V. |journal=The Astronomical Journal |year=2017 |volume=154 |issue=3 |page=94 |doi=10.3847/1538-3881/aa784d |arxiv=1509.05420 |s2cid=119293367 |display-authors=29 |doi-access=free }}</ref>

<ref name=starhorse>{{cite journal |bibcode=2019A&A...628A..94A |title=Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18 |last1=Anders |first1=F. |last2=Khalatyan |first2=A. |last3=Chiappini |first3=C. |last4=Queiroz |first4=A. B. |last5=Santiago |first5=B. X. |last6=Jordi |first6=C. |last7=Girardi |first7=L. |last8=Brown |first8=A. G. A. |last9=Matijevič |first9=G. |last10=Monari |first10=G. |last11=Cantat-Gaudin |first11=T. |last12=Weiler |first12=M. |last13=Khan |first13=S. |last14=Miglio |first14=A. |last15=Carrillo |first15=I. |last16=Romero-Gómez |first16=M. |last17=Minchev |first17=I. |last18=De Jong |first18=R. S. |last19=Antoja |first19=T. |last20=Ramos |first20=P. |last21=Steinmetz |first21=M. |last22=Enke |first22=H. |journal=Astronomy and Astrophysics |volume=628 |pages=A94 |year=2019 |arxiv=1904.11302 |doi=10.1051/0004-6361/201935765 |s2cid = 131780028}}</ref>

}}

{{Stars of Aquarius}}

{{DEFAULTSORT:U Aquarii}}
[[Category:Carbon stars]]
[[Category:R Coronae Borealis variables]]
[[Category:Aquarius (constellation)]]
[[Category:Durchmusterung objects]]
[[Category:Hipparcos objects|108876]]
[[Category:Objects with variable star designations|Aquarii, U]]

Latest revision as of 01:45, 28 November 2023

Not to be confused with Upsilon Aquarii.
U Aquarii

The visual band light curve of U Aquarii, from AAVSO data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Aquarius
Right ascension 22h 03m 19.69905s[2]
Declination −16° 37′ 35.2811″[2]
Apparent magnitude (V) 10.6 to 15.9[3]
Characteristics
Spectral type C-Hd[4]
U−B color index 0.07[5]
B−V color index 0.66[5]
Variable type R CrB[3]
Astrometry
Radial velocity (Rv)+89.49±1.54[6] km/s
Proper motion (μ) RA: 2.780[2] mas/yr
Dec.: −1.907[2] mas/yr
Parallax (π)0.0859 ± 0.0222 mas[2]
Distanceapprox. 38,000 ly
(approx. 12,000 pc)
Details
Mass4.5[7] M☉
Surface gravity (log g)2.28[7] cgs
Temperature5,500[5] K
Metallicity [Fe/H]−0.99[7] dex
Rotational velocity (v sin i)8.4[8] km/s
Other designations
U Aqr, BD−17°6424, HIP 108876, IRAS 22006-1652[9]
Database references
SIMBADdata

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.[3] 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.[5] It appears to lie several kiloparsecs below the galactic plane, and thus may belong to an old stellar population.[4]

The stellar classification of this star is C-Hd,[4] and it is classified as a R Coronae Borealis variable.[3] It is a carbon star with a hydrogen-deficient spectra that also shows evidence of s-process elements,[4] including overabundances of strontium and yttrium, but no barium.[10] This combination of properties is exceptionally rare; only one other example has been found as of 2012.[11] 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.[10] In 1999, U Aqr was proposed to be a Thorne-Zytkow object, instead of being a simple R Coronae Borealis variable.[12]

References[edit]

  1. ^ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. ^ a b c d e 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. ^ 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.
  4. ^ 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.
  5. ^ 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.
  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. ^ a b c 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. ^ 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 (3): 743–752. Bibcode:1985MNRAS.216..743M. doi:10.1093/mnras/216.3.743.
  11. ^ 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.
  12. ^ 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.
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