View source for Astronomy:Chi Eridani

{{short description|Star in the constellation Eridanus}}
{{Starbox begin
 | name = [[Astronomy:Bayer designation|χ Eridani]]}}
{{Starbox observe
 | epoch = [[Astronomy:J2000.0|J2000.0]]
 | equinox = [[Astronomy:J2000.0|J2000.0]] ([[Astronomy:International Celestial Reference System|ICRS]])
 | constell = [[Astronomy:Eridanus (constellation)|Eridanus]]
 | ra = {{RA|01|55|57.45606}}<ref name=GaiaDR2/>
 | dec = {{DEC|−51|36|31.9736}}<ref name=GaiaDR2/>
 | appmag_v = {{nowrap|3.70<ref name=Mermilliod1986/> / 10.7<ref name=Poveda1994/>}}
}}
{{Starbox character
 | class = G8IV<ref name=Torres2006/> or {{nowrap|G8IIIb CNIV}}<ref name=Houk1978/>
 | u-b = +0.46<ref name=Mermilliod1986/>
 | b-v = +0.85<ref name=Mermilliod1986/>
 | r-i = 
}}
{{Starbox astrometry
 | radial_v = –6.30<ref name=Gontcharov2006/>
 | prop_mo_ra = +682.281<ref name=GaiaDR2/>
 | prop_mo_dec = −295.332<ref name=GaiaDR2/>
 | parallax = 57.3774
 | p_error = 0.3291
 | parallax_footnote = <ref name=GaiaDR2/>
 | absmag_v= {{nowrap|2.39 / 9.4}}<ref name=Poveda1994/>
}}
{{Starbox detail
 | source = <ref name=Rains2020/>
 | component1 = A
 | mass = 1.58<ref name=Fuhrmann2012/>
 | radius = {{Val|3.993|0.027}}
 | luminosity = {{val|9.84|0.39}}
 | temperature = {{Val|5115|49|fmt=commas}}
 | gravity = {{Val|3.42|0.10}}
 | metal_fe = {{Val|−0.18|0.07}}
 | rotational_velocity = 4.50
 | age_myr = 
}}
{{Starbox catalog
 | names = {{odlist | B=χ Eri | FK5=68 | GJ=81 | HD=11937 | HIP=9007 | HR=566 | SAO=232573 }}<ref name=SIMBAD/>
}}
{{Starbox reference
|Simbad=chi+Eri
|ARICNS=00163|an=A
|ARICNS2=00164|an2=B
}}
{{Starbox end}}

'''χ Eridani''' (Latinised as '''Chi Eridani''') is a [[Astronomy:Binary star|binary star]]<ref name=Eggleton2008/> system in the [[Astronomy:Constellation|constellation]] [[Astronomy:Eridanus (constellation)|Eridanus]]. It is visible to the naked eye with an [[Astronomy:Apparent visual magnitude|apparent visual magnitude]] of 3.70.<ref name=Mermilliod1986/> The distance to this system, as determined using the [[Astronomy:Stellar parallax|parallax method]], is around 58&nbsp;[[Light year|light year]]s.<ref name=GaiaDR2/> The pair had an angular separation of 5.0&nbsp;[[Arcsecond|arcsecond]]s as of 1994. This corresponds to a projected separation of around 128&nbsp;AU.<ref name=Poveda1994/>

The primary component is an [[Astronomy:Stellar evolution|evolving]] G-type [[Astronomy:Subgiant|subgiant]] star with a [[Astronomy:Stellar classification|stellar classification]] of G8&nbsp;IV.<ref name=Torres2006/> It is about 1.6 times the mass of the Sun and has 4 times the Sun's radius.<ref name=Fuhrmann2012/> The star shines with 10 times the [[Astronomy:Solar luminosity|solar luminosity]] from its [[Astronomy:Stellar atmosphere|outer atmosphere]] at an [[Astronomy:Effective temperature|effective temperature]] of 5,115&nbsp;K.<ref name=Rains2020/> Unusually for a star of this class, it shows a [[Astronomy:Photometry|photometric]] [[Astronomy:Variable star|variability]] of 0.04 in magnitude, which may be due to a previous mass transfer from the secondary companion, or else from an undiscovered third companion.<ref name=Fuhrmann2012/>

The companion is about 7 magnitudes fainter than the primary and may be the source of the [[X-ray astronomy|X
-ray emission]] from this system. This emission has a luminosity of {{Val|504.4e27|u=erg s<sup>−1</sup>}}.<ref name=Fuhrmann2012/>

==References==
{{reflist|refs=

<ref name=GaiaDR2>{{Cite Gaia DR2|4937200425855463936}}</ref>

<ref name=Houk1978>{{cite book
 | last1=Houk | first1=N.
 | title=Michigan catalogue of two-dimensional spectral types for the HD stars
 | volume=2 | date=1978 | publisher=Dept. of Astronomy, University of Michigan
 | bibcode=1978mcts.book.....H }}</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
 | doi=10.1134/S1063773706110065| bibcode=2006AstL...32..759G
 | arxiv=1606.08053 | s2cid=119231169
 }}</ref>

<ref name=Rains2020>{{cite journal
 | title=Precision angular diameters for 16 southern stars with VLTI/PIONIER
 | display-authors=1 | last1=Rains | first1=Adam D.
 | last2=Ireland | first2=Michael J. | last3=White | first3=Timothy R.
 | last4=Casagrande | first4=Luca | last5=Karovicova | first5=I.
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=493 | issue=2 | pages=2377–2394 | date=April 2020
 | arxiv=2004.02343 | bibcode=2020MNRAS.493.2377R 
 | doi=10.1093/mnras/staa282 }}</ref>

<ref name=Eggleton2008>{{citation
 | last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
 | title=A catalogue of multiplicity among bright stellar systems
 | journal=[[Organization:Monthly Notices of the Royal Astronomical Society|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 | s2cid=14878976 | postscript=. }}</ref>

<ref name=Torres2006>{{citation
 | display-authors=1
 | last1=Torres | first1=C. A. O. | last2=Quast | first2=G. R.
 | last3=Da Silva | first3=L. | last4=De La Reza | first4=R.
 | last5=Melo | first5=C. H. F. | last6=Sterzik | first6=M.
 | title=Search for associations containing young stars (SACY). I. Sample and searching method
 | journal=Astronomy and Astrophysics
 | volume=460 | issue=3 | date=December 2006 | pages=695–708
 | doi=10.1051/0004-6361:20065602 | bibcode=2006A&A...460..695T
 | arxiv=astro-ph/0609258 | s2cid=16080025 | postscript=. }}</ref>

<ref name=Fuhrmann2012>{{citation
 | last1=Fuhrmann | first1=K. | last2=Chini | first2=R.
 | title=Multiplicity among F-type Stars
 | journal=The Astrophysical Journal Supplement
 | volume=203 | issue=2 | pages=20 | id=30 | date=2012
 | doi=10.1088/0067-0049/203/2/30 | bibcode=2012ApJS..203...30F
 | postscript=. | doi-access=free }}</ref>

<ref name=Poveda1994>{{citation
 | display-authors=1 | last1=Poveda | first1=A.
 | last2=Herrera | first2=M. A. | last3=Allen | first3=C.
 | last4=Cordero | first4=G. | last5=Lavalley | first5=C.
 | title=Statistical studies of visual double and multiple stars. II. A catalogue of nearby wide binary and multiple systems
 | journal=Revista Mexicana de Astronomía y Astrofísica
 | volume=28 | issue=1 | pages=43–89 | date=April 1994
 | bibcode=1994RMxAA..28...43P | postscript=. }} See pp. 58–59.</ref>

<ref name=Mermilliod1986>{{citation
 | last1=Mermilliod | first1=J.-C.
 | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)
 | journal=Catalogue of Eggen's UBV Data
 | publisher=[[Astronomy:SIMBAD|SIMBAD]] | date=1986 | bibcode=1986EgUBV........0M
 | postscript=. }}</ref>

<ref name=SIMBAD>{{cite simbad
 | title=* chi Eri -- Pre-main sequence Star  
 | access-date=2016-10-27 | postscript=. }}</ref>

}}

{{Stars of Eridanus|state=collapsed}}

{{DEFAULTSORT:Chi Eridani}}
[[Category:G-type subgiants]]
[[Category:Binary stars]]
[[Category:Eridanus (constellation)]]
[[Category:Bayer objects|Eridani, Chi]]
[[Category:Durchmusterung objects]]
[[Category:Gliese and GJ objects|0081]]
[[Category:Henry Draper Catalogue objects|011937]]
[[Category:Hipparcos objects|009007]]
[[Category:Bright Star Catalogue objects|0566]]

{{Sourceattribution|Chi Eridani}}