psi Hydrae
{{Short description|Binary star system in the constellation Hydra}}
{{Starbox begin
| name = Psi Hydrae
}}
{{Starbox observe
| epoch = J2000.0
| constell = Hydra
| dec = {{DEC|−23|07|05.0501}}
}}
{{Starbox character
| r-i =
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|−17.2|0.6}}
| parallax = 14.09
| p_error = 0.48
}}
{{Starbox detail
| source =
| mass =
| metal_fe = {{Val|−0.19|0.04}}
| rotational_velocity =
| age_myr =
}}
{{Starbox catalog
| names = ψ Hya, 45 Hydrae, BD−22°3515, HD 114149, HIP 64166, HR 4958, SAO 181410
}}
{{Starbox reference
| Simbad = psi+Hya
}}
{{Starbox end}}
Psi Hydrae (ψ Hydrae) is a star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 14.09 mas as seen from Earth, it is located around 231 light years away from the Sun. It is faintly visible to the naked eye with an apparent magnitude of 4.97.
System
This is a probable astrometric binary system. The primary, component A, is an evolved giant star with a stellar classification of K0 III. It is a red clump star that is generating energy through the fusion of helium at its core. The measured angular diameter is {{Val|1.39|0.02|u=mas}}, which, at the estimated distance of Psi Hydrae, yields a physical size of about 10.6 times the radius of the Sun. It is radiating 56 times the solar luminosity from its photosphere at an effective temperature of 4,680. K.
Cultural significance
The Kalapalo people of Mato Grosso state in Brazil called this star and β Hya Kafanifani.{{cite book|last=Basso|first=Ellen B. |title=In Favor of Deceit: A Study of Tricksters in an Amazonian Society|publisher=University of Arizona Press|location=Tucson, Arizona|date=1987|page=[https://archive.org/details/infavorofdeceits0000bass/page/360 360]|isbn=0-8165-1022-9|url=https://archive.org/details/infavorofdeceits0000bass|url-access=registration}}
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=. }}
| 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 | year=2012 | postscript=.
| bibcode=2012MNRAS.427..343M | arxiv=1208.2037
| doi=10.1111/j.1365-2966.2012.21873.x | doi-access=free | s2cid=118665352 }}
| last1=Makarov | first1=V. V. | last2=Kaplan | first2=G. H.
| title=Statistical Constraints for Astrometric Binaries with Nonlinear Motion
| journal=The Astronomical Journal | postscript=.
| volume=129 | issue=5 | pages=2420–2427 | date=May 2005
| doi=10.1086/429590 | bibcode=2005AJ....129.2420M | doi-access=free }}
| last1=Alves | first1=David R.
| title=K-Band Calibration of the Red Clump Luminosity
| journal=The Astrophysical Journal
| volume=539 | issue=2 | pages=732–741 | date=August 2000
| doi=10.1086/309278 | bibcode=2000ApJ...539..732A
| arxiv=astro-ph/0003329 | s2cid=16673121
| postscript=. }}
| last1=McWilliam | first1=Andrew
| title=High-resolution spectroscopic survey of 671 GK giants
| journal=Astrophysical Journal Supplement Series
| date=December 1990 | volume=74 | pages=1075–1128
| bibcode=1990ApJS...74.1075M | doi=10.1086/191527
| postscript=. | doi-access=free}}
| display-authors=1 | last1=Richichi | first1=A.
| last2=Percheron | first2=I. | last3=Khristoforova | first3=M.
| title=CHARM2: An updated Catalog of High Angular Resolution Measurements
| journal=Astronomy and Astrophysics | postscript=.
| volume=431 | pages=773–777 | date=February 2005
| issue=2 | doi=10.1051/0004-6361:20042039 | bibcode=2005A&A...431..773R | doi-access=free }}
| first1=Kenneth R. | last1=Lang | title=Astrophysical formulae
| volume=1 | series=Astronomy and astrophysics library | postscript=.
| edition=3rd | publisher=Birkhäuser | date=2006 | isbn=3-540-29692-1
| url=https://books.google.com/books?id=OvTjLcQ4MCQC&pg=PA41
}} The radius (R*) is given by:
:
& = \frac{(71.0\cdot 1.39\cdot 10^{-3})\ \text{AU}}{0.0046491\ \text{AU}/R_{\bigodot}} \\
& \approx 21.2\cdot R_{\bigodot}
\end{align}
| 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=. }}
| last1=Houk | first1=Nancy | last2=Smith-Moore | first2=M.
| title=Michigan catalogue of two-dimensional spectral types for the HD stars
| volume=4 | location=Ann Arbor | year=1978
| publisher=Dept. of Astronomy, University of Michigan
| bibcode=1988mcts.book.....H | 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=* psi Hya
| access-date=2017-03-17 | postscript=. }}
}}
{{Stars of Hydra|state=collapsed}}
{{DEFAULTSORT:Psi Hydrae}}
Category:Horizontal-branch stars