tau2 Hydrae
{{Short description|Binary star system in the constellation Hydra}}
{{DISPLAYTITLE:Tau2 Hydrae}}
{{other stars by Bayer designation|Tau Hydrae{{!}}τ Hydrae}}
{{Starbox begin
| name = Tau2 Hydrae
}}
{{Starbox observe
| epoch = J2000.0
| constell = Hydra
| dec = {{DEC|-01|11|04.7899}}
}}
{{Starbox character
| r-i =
}}
{{Starbox astrometry
| parallax = 6.30
| p_error = 0.72
}}
{{Starbox detail
| source =
| mass =
| gravity =
| metal_fe =
| rotational_velocity = {{Val|54.0|0.6}}
| age_myr =
}}
{{Starbox catalog
| names = Ukdah, τ2 Hya, 32 Hydrae, BD−00°2211, HD 82446, HIP 46776, HR 3787, SAO 136932.
}}
{{Starbox reference
| Simbad = tau02+Hya
}}
{{Starbox end}}
Tau2 Hydrae is a probable astrometric binary star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 6.30 mas as seen from Earth, it is located around 520 light years from the Sun. The brighter component is visible to the naked eye with an apparent visual magnitude of +4.56.
The primary member, component A, is an A-type main sequence star with a stellar classification of A3 V. It is a suspected variable of unknown type, with an amplitude of 0.06 in visual magnitude. The star has around 4.5 times the radius of the Sun and is radiating about 285 times the solar luminosity from its photosphere at an effective temperature of 7,918 K.
References
{{reflist|refs=
| 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 | s2cid=18759600 | postscript=. }}
| title=XHIP: An extended hipparcos compilation
| last1=Anderson | first1=E. | last2=Francis | first2=Ch.
| journal=Astronomy Letters
| volume=38 | issue=5 | pages=331 | year=2012
| bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015
| arxiv=1108.4971 | s2cid=119257644 | postscript=. }}
| title=On the Variability of A3-F0 Luminosity Class III-V Stars
| last1=Adelman | first1=S. J.
| journal=Information Bulletin on Variable Stars
| issue=4969 | page=1 | date=October 2000
| volume=4969 | bibcode=2000IBVS.4969....1A | postscript=. }}
| last1=Pasinetti Fracassini | first1=L. E. | last2=Pastori | first2=L.
| last3=Covino | first3=S. | last4=Pozzi | first4=A.
| title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)
| edition=3rd | journal=Astronomy and Astrophysics
| volume=367 | pages=521–524 | date=February 2001
| doi=10.1051/0004-6361:20000451 | bibcode=2001A&A...367..521P
| arxiv=astro-ph/0012289 | s2cid=425754 | postscript=. }}
| 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 | doi-access=free | bibcode=2008MNRAS.389..869E
| postscript=. |arxiv = 0806.2878 | s2cid=14878976 }}
| display-authors=1 | last1=McDonald | first1=I.
| last2=Zijlstra | first2=A. A. | last3=Boyer | first3=M. L.
| title=Fundamental Parameters and Infrared Excesses of Hipparcos Stars
| journal=Monthly Notices of the Royal Astronomical Society
| volume=427 | issue=1 | pages=343–57 | date=2012
| bibcode=2012MNRAS.427..343M | arxiv=1208.2037
| doi=10.1111/j.1365-2966.2012.21873.x | doi-access=free | s2cid=118665352 | postscript=. }}
| last1=de Bruijne | first1=J. H. J. | last2=Eilers | first2=A.-C.
| title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project
| journal=Astronomy & Astrophysics
| volume=546 | id=A61 | pages=14 | date=October 2012
| doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D
| arxiv=1208.3048 | s2cid=59451347 | postscript=. }}
| display-authors=1
| last1=Díaz | first1=C. G. | last2=González | first2=J. F.
| last3=Levato | first3=H. | last4=Grosso | first4=M.
| title=Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum
| journal=Astronomy & Astrophysics
| volume=531 | page=A143 |date=July 2011
| doi=10.1051/0004-6361/201016386 | bibcode=2011A&A...531A.143D
| arxiv=1012.4858 | s2cid=119286673 | postscript=. }}
| last1=Mermilliod | first1=J.-C.
| title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)
| journal=Catalogue of Eggen's UBV Data
| year=1986 | publisher=SIMBAD
| bibcode=1986EgUBV........0M | postscript=. }}
| title=* tau02 Hya
| access-date=2017-03-22 | postscript=. }}
}}
{{Stars of Hydra|state=collapsed}}
{{DEFAULTSORT:Tau2 Hydrae}}
Category:A-type main-sequence stars
Category:Hydra (constellation)