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{{Starbox begin}}
{{starbox short
{{Starbox observe
|constell= [[Hydra (constellation)|Hydra]]
| epoch = J2000
|name= U Hydrae
| constell = [[Hydra (constellation)|Hydra]]
|type= C<ref name=SIMBAD>SIMBAD, [http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=U+Hydrae&submit=SIMBAD+search U Hydrae] (accessed 29 September 2012)</ref>
|ra= {{RA|10|37|33.27295}}<ref name=SIMBAD/>
| ra = {{RA|10|37|33.27295}}<ref name=vanLeeuwen2007/>
|dec= {{DEC|-13|23|04.3529}}<ref name=SIMBAD/>
| dec = {{DEC|−13|23|04.3529}}<ref name=vanLeeuwen2007/>
| appmag_v = 4.89<ref name=Anderson2012/>
|names={{odlist|V=U Hya|BD=-12° 3218|HD=92055|HIP=52009|HR=4163|SAO=156110}}
}}
}}
{{Starbox character
'''U Hydrae''' ('''U Hya''') is a [[carbon star]] in the [[constellation]] [[Hydra (constellation)|Hydra]]. It is also a [[variable star]], with its brightness ranging from 4.7 to 5.2 over a 450-day period, with some irregularity.<ref name="Monks">{{cite book|last1=Monks|first1=Neale|title=Go-To Telescopes Under Suburban Skies|date=2010|publisher=Springer|isbn=978-1-4419-6851-7|page=65|url=https://books.google.com/books?id=waO6tUtfblsC&pg=PA65}}</ref>
| type = [[asymptotic giant branch|AGB]]<ref name=Rau2017/>
| class = {{nowrap|C-N5 C2 5-}}<ref name=barnbaum1996/>
| b-v = {{Val|2.80|0.51}}<ref name=Anderson2012/>
| u-b =
| variable = [[semiregular variable star|SRb]]<ref name=Samus2017/>
}}
{{Starbox astrometry
| radial_v = {{Val|−25.8|1.7}}<ref name=Gontcharov2006/>
| prop_mo_ra = +42.59<ref name=vanLeeuwen2007/>
| prop_mo_dec = −37.72<ref name=vanLeeuwen2007/>
| parallax = 4.80
| p_error = 0.23
| parallax_footnote = <ref name=vanLeeuwen2007/>
| absmag_v = −1.70<ref name=Anderson2012/>
}}
{{Starbox detail
| source =
| mass =
| radius = {{Val|96.0|9.1|16.5}}<ref name=GaiaDR2/>
| luminosity = {{Val|1459|148|fmt=commas}}<ref name=GaiaDR2/>
| luminosity_bolometric = 3,476<ref name=Rau2017/>
| temperature = {{Val|3641|359|161|fmt=commas}}<ref name=GaiaDR2/>
| gravity =
| metal_fe = −0.1<ref name=Lambert1986/>
| rotational_velocity =
| age_myr =
}}
{{Starbox catalog
| names = {{odlist | V=U Hya | BD=−12°3218 | HD=92055 | HIP=52009 | HR=4163 | SAO=156110 }}<ref name=SIMBAD/>
}}
{{Starbox reference
| Simbad=U+Hya
}}
{{Starbox end}}

'''U Hydrae''' is a single<ref name=Eggleton2008/> [[star]] in the [[celestial equator|equatorial]] [[constellation]] of [[Hydra (constellation)|Hydra]], near the northern constellation border with [[Sextans]]. It is a [[semiregular variable star]] of sub-type SRb,<ref name=Samus2017/> with its brightness ranging from visual magnitude (V) 4.7 to 5.2 over a 450-day period, with some irregularity.<ref name="Monks"/> This object is located at a distance of approximately 680&nbsp;[[light year]]s from the [[Sun]] based on [[stellar parallax|parallax]].<ref name=vanLeeuwen2007/> It is drifting closer with a [[radial velocity]] of −26&nbsp;km/s.<ref name=Gontcharov2006/>

This is a carbon-rich [[red giant star]] on the [[asymptotic giant branch]]<ref name=Rau2017/> – a [[carbon star]] – with [[s-process]] elements appearing in the [[stellar spectrum|spectrum]]. It has a [[stellar classification]] of {{nowrap|C-N5}} with a carbon star class of {{nowrap|C2 5-}}.<ref name=barnbaum1996/> The star is losing mass at the rate of {{Val|1.2e−7|ul=solar mass}}&middot;yr<sup>−1</sup>, with an outflow velocity of {{val|6.9|u=km/s}}. [[Technetium star|Technetium]] has been detected in the spectrum, suggesting the star has experienced its third [[dredge-up]] episode due to thermal pulses of the [[helium fusion|helium-burning]] shell some time within the last 100,000&nbsp;years.<ref name=Izumiura2011/>

An [[ultraviolet astronomy|ultraviolet]] (UV) excess has been detected coming from an extended elliptical ring that surrounds this star. It has a mean [[angular radius]] of {{Val|110|ul=arcsecond}} and lines up with a detached shell of dusty material that was previously detected in the [[infrared astronomy|infrared]] band. The material was most likely ejected from the star due to mass loss episodes. The probably cause of the UV emission is from the movement of the star through space and possibly shock-excited molecules of H<sub>2</sub>. The emission does not show a bow-shock-like structure.<ref name=Sanchez2015/>


==References==
==References==
{{reflist}}
{{reflist|30em|refs=


<ref name=GaiaDR2>{{cite DR2|3751290548758098688}}</ref>
{{Stars of Hydra}}


<ref name=SIMBAD>{{cite simbad | title=U Hya | access-date=19 March 2016}}</ref>
[[Category:Hydra (constellation)]]

<ref name=Lambert1986>{{cite journal
| title=The Chemical Composition of Carbon Stars. I. Carbon, Nitrogen, and Oxygen in 30 Cool Carbon Stars in the Galactic Disk
| last1=Lambert | first1=David L. | last2=Gustafsson | first2=Bengt
| last3=Eriksson | first3=Kjell | last4=Hinkle | first4=Kenneth H.
| display-authors=1 | journal=Astrophysical Journal Supplement
| volume=62 | page=373 | date=October 1986
| doi=10.1086/191145 | bibcode=1986ApJS...62..373L }}</ref>

<ref name=Anderson2012>{{cite journal
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters | arxiv=1108.4971
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 }}</ref>

<ref name=vanLeeuwen2007>{{cite journal
| title=Validation of the new Hipparcos reduction
| last1=van Leeuwen | first1=F.
| journal=Astronomy and Astrophysics
| volume=474 | issue=2 | pages=653–664 | date=2007
| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 }}</ref>

<ref name=Samus2017>{{cite journal
| display-authors=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.
| title=General Catalogue of Variable Stars
| version=5.1 | journal=Astronomy Reports
| year=2017 | volume=61 | issue=1 | pages=80–88
| bibcode=2017ARep...61...80S | doi=10.1134/S1063772917010085 }}</ref>

<ref name=Gontcharov2006>{{cite journal
| last1=Gontcharov | first1=G. A.
| title=Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system
| journal=Astronomy Letters
| volume=32| issue=11| pages=759–771| date=November 2006
| bibcode=2006AstL...32..759G | arxiv=1606.08053
| doi=10.1134/S1063773706110065 }}</ref>

<ref name=Eggleton2008>{{cite journal
| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
| title=A catalogue of multiplicity among bright stellar systems
| journal=Monthly Notices of the Royal Astronomical Society
| volume=389 | issue=2 | pages=869–879 | date=September 2008
| doi=10.1111/j.1365-2966.2008.13596.x
| bibcode=2008MNRAS.389..869E | arxiv=0806.2878 }}</ref>

<ref name="Monks">{{cite book
| last1=Monks | first1=Neale
| title=Go-To Telescopes Under Suburban Skies
| date=2010 | publisher=Springer
| isbn=978-1-4419-6851-7 | page=65
| url=https://books.google.com/books?id=waO6tUtfblsC&pg=PA65 }}</ref>

<ref name=Sanchez2015>{{cite journal
| title=First Detection of Ultraviolet Emission from a Detached Dust Shell: Galaxy Evolution Explorer Observations of the Carbon Asymptotic Giant Branch Star U Hya
| last1=Sanchez | first1=Enmanuel | last2=Montez | first2=Rodolfo, Jr.
| last3=Ramstedt | first3=Sofia | last4=Stassun | first4=Keivan G.
| display-authors=1 | journal=The Astrophysical Journal Letters
| volume=798 | issue=2 | id=L39 | pages=5 | date=January 2015
| arxiv=1412.7542 | bibcode=2015ApJ...798L..39S
| doi=10.1088/2041-8205/798/2/L39 }}</ref>

<ref name=Rau2017>{{cite journal
| title=The adventure of carbon stars. Observations and modeling of a set of C-rich AGB stars
| last1=Rau | first1=G. | last2=Hron | first2=J.
| last3=Paladini | first3=C. | last4=Aringer | first4=B.
| last5=Eriksson | first5=K. | last6=Marigo | first6=P.
| last7=Nowotny | first7=W. | last8=Grellmann | first8=R.
| display-authors=1 | journal=Astronomy & Astrophysics
| volume=600 | id=A92 | pages=21 | date=April 2017
| arxiv=1701.04331 | bibcode=2017A&A...600A..92R
| doi=10.1051/0004-6361/201629337 }}</ref>

<ref name=Izumiura2011>{{cite journal
| title=Extended dust shell of the carbon star U Hydrae observed with AKARI
| display-authors=1 | last1=Izumiura | first1=H.
| last2=Ueta | first2=T. | last3=Yamamura | first3=I.
| last4=Matsunaga | first4=N. | last5=Ita | first5=Y.
| last6=Matsuura | first6=M. | last7=Nakada | first7=Y.
| last8=Fukushi | first8=H. | last9=Mito | first9=H.
| last10=Tanabé | first10=T. | last11=Hashimoto | first11=O.
| journal=Astronomy & Astrophysics
| volume=528 | id=A29 | pages=14 | date=April 2011
| doi=10.1051/0004-6361/201015163 | bibcode=2011A&A...528A..29I }}</ref>

<ref name=barnbaum1996>{{cite journal
| display-authors=1 | last1=Barnbaum | first1=Cecilia
| last2=Stone | first2=Remington P. S. | last3=Keenan | first3=Philip C.
| title=A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars
| journal=Astrophysical Journal Supplement
| volume=105 | pages=419 |year=1996
| bibcode=1996ApJS..105..419B | doi=10.1086/192323 }}</ref>

}}

{{Stars of Horologium}}
<!-- Properties -->
[[Category:C-type stars]]
[[Category:C-type stars]]
[[Category:Asymptotic-giant-branch stars]]
[[Category:Objects with variable star designations|Hydrae, U]]
[[Category:Semiregular variable stars]]
<!-- Identifiers -->
[[Category:Hydra (constellation)]]
[[Category:Durchmusterung objects]]
[[Category:Durchmusterung objects]]
[[Category:Henry Draper Catalogue objects|092055]]
[[Category:Henry Draper Catalogue objects|092055]]
[[Category:Hipparcos objects|052009]]
[[Category:Hipparcos objects|052009]]
[[Category:HR objects|4163]]
[[Category:HR objects|4163]]
[[Category:Objects with variable star designations|Hydrae, U]]
[[Category:Asymptotic-giant-branch stars]]
[[Category:Semiregular variable stars]]


{{var-star-stub}}

Revision as of 18:27, 17 February 2020

U Hydrae
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension 10h 37m 33.27295s[1]
Declination −13° 23′ 04.3529″[1]
Apparent magnitude (V) 4.89[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type C-N5 C2 5-[4]
B−V color index 2.80±0.51[2]
Variable type SRb[5]
Astrometry
Radial velocity (Rv)−25.8±1.7[6] km/s
Proper motion (μ) RA: +42.59[1] mas/yr
Dec.: −37.72[1] mas/yr
Parallax (π)4.80 ± 0.23 mas[1]
Distance680 ± 30 ly
(208 ± 10 pc)
Absolute magnitude (MV)−1.70[2]
Details
Radius96.0+9.1
−16.5[7] R☉
Luminosity1,459±148[7] L☉
Luminosity (bolometric)3,476[3] L☉
Temperature3,641+359
−161[7] K
Metallicity [Fe/H]−0.1[8] dex
Other designations
U Hya, BD−12°3218, HD 92055, HIP 52009, HR 4163, SAO 156110[9]
Database references
SIMBADdata

U Hydrae is a single[10] star in the equatorial constellation of Hydra, near the northern constellation border with Sextans. It is a semiregular variable star of sub-type SRb,[5] with its brightness ranging from visual magnitude (V) 4.7 to 5.2 over a 450-day period, with some irregularity.[11] This object is located at a distance of approximately 680 light years from the Sun based on parallax.[1] It is drifting closer with a radial velocity of −26 km/s.[6]

This is a carbon-rich red giant star on the asymptotic giant branch[3] – a carbon star – with s-process elements appearing in the spectrum. It has a stellar classification of C-N5 with a carbon star class of C2 5-.[4] The star is losing mass at the rate of 1.2×10−7 M☉·yr−1, with an outflow velocity of 6.9 km/s. Technetium has been detected in the spectrum, suggesting the star has experienced its third dredge-up episode due to thermal pulses of the helium-burning shell some time within the last 100,000 years.[12]

An ultraviolet (UV) excess has been detected coming from an extended elliptical ring that surrounds this star. It has a mean angular radius of 110″ and lines up with a detached shell of dusty material that was previously detected in the infrared band. The material was most likely ejected from the star due to mass loss episodes. The probably cause of the UV emission is from the movement of the star through space and possibly shock-excited molecules of H2. The emission does not show a bow-shock-like structure.[13]

References

  1. ^ a b c d e f van Leeuwen, F. (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. ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015.
  3. ^ a b c Rau, G.; et al. (April 2017). "The adventure of carbon stars. Observations and modeling of a set of C-rich AGB stars". Astronomy & Astrophysics. 600: 21. arXiv:1701.04331. Bibcode:2017A&A...600A..92R. doi:10.1051/0004-6361/201629337. A92.
  4. ^ a b Barnbaum, Cecilia; et al. (1996). "A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars". Astrophysical Journal Supplement. 105: 419. Bibcode:1996ApJS..105..419B. doi:10.1086/192323.
  5. ^ a b Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
  6. ^ a b Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. ^ a b c 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.
  8. ^ Lambert, David L.; et al. (October 1986). "The Chemical Composition of Carbon Stars. I. Carbon, Nitrogen, and Oxygen in 30 Cool Carbon Stars in the Galactic Disk". Astrophysical Journal Supplement. 62: 373. Bibcode:1986ApJS...62..373L. doi:10.1086/191145.
  9. ^ "U Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 March 2016.
  10. ^ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x.
  11. ^ Monks, Neale (2010). Go-To Telescopes Under Suburban Skies. Springer. p. 65. ISBN 978-1-4419-6851-7.
  12. ^ Izumiura, H.; et al. (April 2011). "Extended dust shell of the carbon star U Hydrae observed with AKARI". Astronomy & Astrophysics. 528: 14. Bibcode:2011A&A...528A..29I. doi:10.1051/0004-6361/201015163. A29.
  13. ^ Sanchez, Enmanuel; et al. (January 2015). "First Detection of Ultraviolet Emission from a Detached Dust Shell: Galaxy Evolution Explorer Observations of the Carbon Asymptotic Giant Branch Star U Hya". The Astrophysical Journal Letters. 798 (2): 5. arXiv:1412.7542. Bibcode:2015ApJ...798L..39S. doi:10.1088/2041-8205/798/2/L39. L39.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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