{{Short description|Multiple star system in the constellation Libra}} {{DISPLAYTITLE:Iota<sup>1</sup> Librae}} {{other stars by Bayer designation|Iota Librae{{!}}ι Librae}} {{Starbox begin | name=Iota<sup>1</sup> Librae }} {{Starbox image | image = {{Location mark |image=Libra constellation map.svg|alt=|float=center|width=280 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=Iota1 Librae |x=500|y=525 }} | caption = Location of ι<sup>1</sup> Librae (circled in red) }} {{Starbox observe | epoch=J2000 | constell=[[Libra (constellation)|Libra]] | ra= {{RA|15|12|13.29025}}<ref name=vanLeeuwen2007/> | dec= {{DEC|−19|47|30.1592}}<ref name=vanLeeuwen2007/> | appmag_v=+4.54<ref name=SIMBAD/><br>(5.1 + 5.6 + 10.4 + 10.9)<ref name=Tokovinin2018/> }} {{Starbox character | class=B9IVpSi + B9<ref name=Eggleton2008/> + G5IV<ref name=Tokovinin2018/> | b-v=−0.08<ref name=SIMBAD/> | u-b=−0.38<ref name=SIMBAD/> | variable = [[Alpha2 Canum Venaticorum variable|Alpha2 Canum Venaticorum]] }} {{Starbox astrometry | radial_v=−11.6<ref name=SIMBAD/> | prop_mo_ra=−35.40<ref name=vanLeeuwen2007/> | prop_mo_dec=−32.79<ref name=vanLeeuwen2007/> | parallax=8.59 | parallax_footnote=<ref name=vanLeeuwen2007/> | p_error=0.25 | absmag_v=−0.79<ref name=Anderson2012/> }} {{Starbox relpos | reference = <ref name=Tokovinin2018/> | primary = A | component = BC | angdistsec = 57.8 | posang = 111 }} {{Starbox orbit | primary = Aa | name = Ab | reference = <ref name=Mason2023/> | period = {{Val|23.512|0.026}} | axis = {{Val|0.12932|0.00064}} | eccentricity = {{Val|0.2440|0.0029}} | inclination = {{Val|154.2|1.0}} | node = {{Val|173.8|2.3}} | periastron = {{Val|1971.034|0.076|fmt=none}} | periarg = {{Val|340.1|2.8}} | k1 = 3.4<ref name=Pourbaix2004/> }} {{Starbox relpos | reference = <ref name=Tokovinin2018/> | primary = B | component = C | angdistsec = 2.058 | posang = 111 }} {{Starbox detail | source =<ref name=Tokovinin2018/> | component1 = Aa | mass = 3.61 | component2 = Ab | mass2 = 3.12 }} {{Starbox detail|no_heading=y | component1 = B | mass = 0.98 | component2 = C | mass2 = 0.91 }} {{Starbox catalog | names = {{odlist | B=ι<sup>1</sup>&nbsp;Lib | F=24&nbsp;Librae | BD=−19°4047 | HD=134759 | HIP=74392 | HR=5652 | SAO=159090 | WDS=J15122-1948A }}<ref name=SIMBAD>{{cite simbad |title=iot01 Lib |accessdate=2017-12-16}}</ref> }} {{Starbox reference |Simbad=iot+Lib }} {{Starbox end}} '''Iota<sup>1</sup> Librae''' is a quadruple<ref name=Eggleton2008/> [[star system]] in the [[constellation]] [[Libra (constellation)|Libra]]. Its name is a [[Bayer designation]] that is [[Romanization of Greek|Latinized]] from {{nobr|'''ι<sup>1</sup> Librae'''}}, and abbreviated {{nobr|Iota<sup>1</sup> Lib}} or {{nobr|ι<sup>1</sup> Lib}}. Its [[apparent magnitude]] is 4.54. It is located 379 [[light years]] from earth.<ref name=Vizier>[http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ50573aac4cd&-out.add=.&-source=V/137C/XHIP&recno=74147 Extended Hipparcos Compilation (XHIP) (+ Anderson, 2012)]</ref>

== Visibility == Due to its southern location, although the star can be seen from most regions of the earth, observers in the southern hemisphere are more advantaged. Near [[Antarctica]], it appears [[Circumpolar star|circumpolar]], while it always remains invisible only in the vicinity of the [[Arctic Circle]]. Its magnitude of 4.5 means that [[naked eye]] visibility is dependent on a sky sufficiently free from the effects of [[light pollution]].

The best time for observation in the evening sky falls in the months between May and September; from both hemispheres of the period of visibility remains approximately the same, thanks to the position of the star not far from the celestial equator.

== Physical == [[File:Iota1LibLightCurve.png|thumb|left|A [[light curve]] for Iota<sup>1</sup> Librae plotted from ''[[STEREO]]'' data, adapted from Wraight ''et al.'' (2012)<ref name="Wraight"/>]] Iota<sup>1</sup> Librae is a quadruple star system.<ref name=Eggleton2008/> The inner pair, designated components Aa and Ab, form a [[spectroscopic binary]]<ref name=Pourbaix2004/> with an [[orbital period]] of 23.512&nbsp;years and an [[orbital eccentricity|eccentricity]] of 0.2440.<ref name=Mason2023/> The brighter member has a [[stellar classification]] of {{nowrap|B9 IVp Si}},<ref name=Eggleton2008/> indicating it is a [[B-type star|B-type]] [[subgiant star]] with an overabundance of [[silicon]] in the [[photosphere]]. It is a [[variable star]] of the [[Alpha2 Canum Venaticorum variable|Alpha2 Canum Venaticorum]] type with a magnitude that varies from 4.53 to 4.56, while its spectrum likewise shows variability.<ref name=Vizier2>[http://vizier.u-strasbg.fr/viz-bin/VizieR-5?-ref=VIZ50573aac4cd&-out.add=.&-source=B/gcvs/nsv_cat&recno=6981 General Catalogue of Variable Stars (Samus + 2007-2012)]</ref> The secondary component is of class B9.<ref name=Eggleton2008/> The two stars are very close together (0.129 [[arcsecond|arcsec]] away), respectively of magnitude 5.10 and 5.60.<ref name=Tokovinin2018/>

The two other stars are the components C and D; separated by 57.8" from AB and 2.058" from each other. The combined spectrum is G5IV, and each star has masses of 0.98 and 0.91 solar masses, and magnitudes 10.40 and 10.90, respectively.<ref name=Tokovinin2018/>

Due to its position on the ecliptic, it is sometimes obscured by the Moon or planets. A lunar occultation took place April 4, 2012.<ref name=OATO>{{Cite web | url = http://www.oato.inaf.it/index.php?option=com_events&task=view_detail&agid=2141&year=2012&month=04&day=09&Itemid=340&catids=87 | title = Moon occults ι Librae (2012-04-09 02:03 CEST) | publisher = [[Turin Astronomical Observatory]] | accessdate = March 23, 2012 | url-status = dead | archiveurl = https://archive.today/20130413060144/http://www.oato.inaf.it/index.php?option=com_events&task=view_detail&agid=2141&year=2012&month=04&day=09&Itemid=340&catids=87 | archivedate = April 13, 2013 }}</ref>

== References == <references>

<ref name="Wraight">{{citation | last1=Wraight |first1=K. T. |last2=Fossati |first2=L. | last3=Netopil |first3=M. |last4=Paunzen |first4=E. | last5=Rode-Paunzen |first5=M. |last6=Bewsher |first6=D. | last7=Norton |first7=A. J. |last8=White |first8=Glenn J. | title=A photometric study of chemically peculiar stars with the STEREO satellites – I. Magnetic chemically peculiar stars | journal=Monthly Notices of the Royal Astronomical Society |date=February 2012 | volume=420 |issue=1 |pages=757–772 |doi=10.1111/j.1365-2966.2011.20090.x |bibcode=2012MNRAS.420..757W |doi-access=free |arxiv=1110.6283 }}</ref>

<ref name=Tokovinin2018>{{Citation |last=Tokovinin |first=Andrei |date=2018-03-01 |title=The Updated Multiple Star Catalog |bibcode=2018ApJS..235....6T |journal=The Astrophysical Journal Supplement Series |volume=235 |issue=1 |pages=6 |doi=10.3847/1538-4365/aaa1a5 |doi-access=free |arxiv=1712.04750 |issn=0067-0049 | postscript=. }} [https://vizier.cds.unistra.fr/viz-bin/VizieR?-source=J/ApJS/235/6&ID=15122-1948 Iota1 Librae's database entry] at [[VizieR]].</ref>

<ref name=vanLeeuwen2007>{{citation | first=F. | last=van Leeuwen | date=November 2007 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | postscript=. | arxiv=0708.1752 | s2cid=18759600 }}</ref>

<ref name=Mason2023>{{Citation |last1=Mason |first1=Brian D. |last2=Tokovinin |first2=Andrei |last3=Mendez |first3=Rene A. |last4=Costa |first4=Edgardo |date=October 2023 |title=Speckle Interferometry at SOAR in 2022 |bibcode=2023AJ....166..139M |journal=The Astronomical Journal |language=en |volume=166 |issue=4 |pages=139 |doi=10.3847/1538-3881/acedaf |doi-access=free |issn=0004-6256}}.</ref>

<ref name=Anderson2012>{{citation | 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=. }}</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=[[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 }}</ref>

<ref name=Pourbaix2004>{{citation | display-authors=1 | last1=Pourbaix | first1=D. | last2=Tokovinin | first2=A. A. | last3=Batten | first3=A. H. | last4=Fekel | first4=F. C. | last5=Hartkopf | first5=W. I. | last6=Levato | first6=H. | last7=Morrell | first7=N. I. | last8=Torres | first8=G. | last9=Udry | first9=S. | year=2004 | pages=727–732 | volume=424 | title=SB9: The Ninth Catalogue of Spectroscopic Binary Orbits | journal=Astronomy & Astrophysics | bibcode=2004A&A...424..727P | doi=10.1051/0004-6361:20041213 | postscript=. | arxiv=astro-ph/0406573| s2cid=119387088 }}</ref>

</references>

== External links == * [http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Iota+Librae&submit=display+all+measurements Simbad archive]

{{Stars of Libra}}

[[Category:Libra (constellation)]] [[Category:B-type subgiants]] [[Category:Bayer objects|Librae, Iota1]] [[Category:Alpha2 Canum Venaticorum variables]] [[Category:Multiple star systems|4]] [[Category:Flamsteed objects|Librae, 24]] [[Category:Durchmusterung objects|BD-19 4047]] [[Category:Hipparcos objects|074392]] [[Category:Henry Draper Catalogue objects|134759]] [[Category:Bright Star Catalogue objects|5652]]