{{Short description|Star in the constellation Draco}} {{Starbox begin | name=φ Draconis }} {{Starbox image | image= {{Location mark |image=Draco constellation map.svg|alt=|float=center|width=260 |label=|position=right |mark=Red circle.svg|mark_width=10|mark_link=φ Draconis |x=308|y=524 }} |caption=Location of φ Draconis (circled) }} {{Starbox observe | epoch = J2000 | ra = {{RA|18|20|45.43224}}<ref name="LEEUWEN"/> | dec = {{DEC|+71|20|16.1499}}<ref name="LEEUWEN"/> | appmag_v = 4.22<ref name=gcvs/> | constell = [[Draco (constellation)|Draco]] }} {{Starbox character | class = B8VpSi<ref name=mk/> + A4V + B9V<ref name=liska/> | b-v = −0.10<ref name="MERMILLIOD"/> | u-b = −0.38<ref name="MERMILLIOD"/> | variable = [[Alpha2 Canum Venaticorum variable|α<sup>2</sup> CVn]]<ref name=gcvs/> }} {{Starbox astrometry | radial_v=−16.44<ref name=kochukhov2022/> | prop_mo_ra=−5.03<ref name="LEEUWEN"/> | prop_mo_dec=+37.86<ref name="LEEUWEN"/> | parallax=10.77 | p_error=0.38 | parallax_footnote=<ref name="LEEUWEN"/> | absmag_v= {{val|−0.74}} ({{val|−0.48}}/{{val|+0.94}})<ref name=liska/> }} {{Starbox orbit | reference = <ref name=liska/> | primary = A | name = B | period = 307.8 | eccentricity = 0.752 | inclination = 95.6 | axis = 0.965 | axis_unitless = {{val|89.60|ul=au}} }} {{Starbox orbit | reference = <ref name=kochukhov2022/> | primary = Aa | name = Ab | period_unitless = {{val|127.914|ul=days}} | eccentricity = 0.6725 | inclination = 48 | axis = | axis_unitless = | k1 = 33.87 }} {{Starbox detail | component1 = Aa | mass = 3.3<ref name=liska/> | radius = {{val|2.7|0.2}}<ref name=aaa334_181/> | luminosity = 107<ref name=aaa334_181/> | temperature = 11,429<ref name=aaa334_181/> | metal_fe = | gravity = {{val|4.21|0.08}}<ref name=aaa334_181/> | rotational_velocity = 81.5<ref name=kochukhov2022/> | rotation = 1.7165<ref name=kochukhov2022/> | age_myr = 245<ref name=liska/> | component2 = Ab | mass2 = 1.36<ref name=msc/> }} {{Starbox detail|no_heading=y | component1 = B | mass = 2.25<ref name=msc/> | age_myr = 330<ref name=liska/> }} {{Starbox catalog | names=[[Bayer designation|φ Dra]], [[Flamsteed designation|43 Dra]], [[Bonner Durchmusterung|BD]]+71°889, [[Catalog of Components of Double and Multiple Stars|CCDM]] J18208+7120AB, [[Boss General Catalogue|GC]] 25114, [[Henry Draper Catalogue|HD]] 170000, [[Hipparcos catalogue|HIP]] 89908, [[Bright Star Catalogue|HR]] 6920, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 9084 }} {{Starbox reference | Simbad=HD+170000 }} {{Starbox end}}
'''Phi Draconis''' (φ Dra / φ Draconis) is a fourth-magnitude [[variable star]] in the [[constellation]] [[Draco (constellation)|Draco]]. It has the [[Flamsteed designation]] '''43 Draconis'''. It is also a [[triple star]] system where the brightest component is a [[Chemically peculiar star|chemically peculiar]] [[Ap star]].
[[File:PhiDraLightCurve.png|thumb|left|A [[light curve]] for Phi Draconis, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data<ref name=MAST/>]] The brightness of φ Draconis varies by about 0.04 of a [[magnitude (astronomy)|magnitude]] every 1.7 days. This is due to very strong magnetic fields at the surface of the star, and it is classified as an [[Alpha2 Canum Venaticorum variable|α<sup>2</sup> Canum Venaticorum]] variable.<ref name=gcvs/>
φ Draconis is a multiple [[star system]] containing three stars. The inner pair form a single-lined [[spectroscopic binary]] in an eccentric 128-day orbit. The outermost star orbits the inner pair every 308 years. The outer pair can be resolved visually and have a [[semi-major axis]] of {{val|0.752|ul=″}}. A fourth component, C, is also listed in multiple star catalogues, but is only a chance alignment with the triple system.<ref name=liska/>
Phi Draconis Aa is a [[main-sequence]] Ap star with a spectral class of B8. The main abundance excess is silicon, although iron and chromium and also notably elevated.<ref name=prvak/>
In [[Chinese astronomy]], φ Draconis is called 柱史 ([[Pinyin]]: Zhùshǐ), meaning ''Official of Royal Archives'', because this star is marking itself and stand alone in ''Official of Royal Archives'' [[Asterism (astronomy)|asterism]], [[Purple Forbidden enclosure]] (see: [[Chinese constellations]]).<ref>{{in lang|zh}} [http://aeea.nmns.edu.tw/2006/0606/ap060610.html AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 10 日] {{Webarchive|url=https://web.archive.org/web/20110521234349/http://aeea.nmns.edu.tw/2006/0606/ap060610.html |date=2011-05-21 }}</ref>
== References == <references> <ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=8 December 2021}}</ref>
<ref name=liska>{{cite journal|bibcode=2016MNRAS.461..939L|title=Analysis of the multiple system with chemically peculiar component φ Draconis|journal=Monthly Notices of the Royal Astronomical Society|volume=461|issue=1|pages=939–947|last1=Liška|first1=J.|year=2016|doi=10.1093/mnras/stw1355|arxiv=1606.01333|doi-access=free}}</ref>
<ref name="MERMILLIOD">{{cite journal | last1=Mermilliod | first1=J.-C. | title=Compilation of Eggen's UBV data, transformed to UBV (unpublished) | journal=Catalogue of Eggen's UBV Data | pages=0 | date=1986 | bibcode=1986EgUBV........0M }}</ref>
<ref name="LEEUWEN">{{cite journal | title=Hipparcos, the New Reduction | last1=van Leeuwen | first1=F. |date=November 2007 | format=[[VizieR]] | pages=653–664 | issue=2 | volume=474 | url=http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%2089908 | doi=10.1051/0004-6361:20078357 | journal=Astronomy and Astrophysics | bibcode=2007A&A...474..653V | access-date=2010-11-22 |arxiv = 0708.1752 | s2cid=18759600 }}</ref>
<ref name=aaa334_181>{{cite journal | last1=North | first1=P. | title=Do SI stars undergo any rotational braking? | journal=Astronomy and Astrophysics | volume=334 | pages=181–187 |date=June 1998 | bibcode=1998A&A...334..181N |arxiv = astro-ph/9802286 }}</ref>
<ref name=mk>{{cite journal|bibcode= 2014AJ....147...80G |title= An Expert Computer Program for Classifying Stars on the MK Spectral Classification System |journal= The Astronomical Journal |volume= 147 |issue= 4 |pages= 80 |last1= Gray |first1= R. O. |last2= Corbally |first2= C. J. |year= 2014 |doi=10.1088/0004-6256/147/4/80|s2cid= 28584130 |doi-access= free }}</ref>
<ref name=gcvs>{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}</ref>
<ref name=prvak>{{cite journal|bibcode=2015A&A...584A..17P|title=Modelling of variability of the chemically peculiar star ϕ Draconis|journal=Astronomy and Astrophysics|volume=584|pages=A17|last1=Prvák|first1=M.|last2=Liška|first2=J.|last3=Krtička|first3=J.|last4=Mikulášek|first4=Z.|last5=Lüftinger|first5=T.|year=2015|doi=10.1051/0004-6361/201526647|arxiv=1510.01192|doi-access=free}}</ref>
<ref name=kochukhov2022>{{cite journal |bibcode=2022MNRAS.510.5821K |title=Magnetic field topology, chemical spot distributions, and photometric variability of the Ap star φ Draconis |last1=Kochukhov |first1=O. |last2=Papakonstantinou |first2=N. |last3=Neiner |first3=C. |journal=Monthly Notices of the Royal Astronomical Society |year=2022 |volume=510 |issue=4 |page=5821 |doi=10.1093/mnras/stac066 |doi-access=free |arxiv=2201.02554 }}</ref>
<ref name=msc>{{Cite journal|last=Tokovinin|first=Andrei|date=2018-03-01|title=The Updated Multiple Star Catalog|journal=[[The Astrophysical Journal Supplement Series]]|volume=235|issue=1|pages=6|doi=10.3847/1538-4365/aaa1a5|issn=0067-0049|arxiv=1712.04750|bibcode=2018ApJS..235....6T|s2cid=119047709 |doi-access=free }}</ref> </references>
== External links == *Jim Kaler's Stars, University of Illinois: [http://stars.astro.illinois.edu/sow/phidra.html PHI DRA (Phi Draconis)] *An Atlas of the Universe: [http://www.atlasoftheuniverse.com/orbits.html Multiple Star Orbits]
{{Stars of Draco}} {{Sky|18|20|45.43|+|71|20|16.13|1000000}}
[[Category:Draco (constellation)]] [[Category:Ap stars]] [[Category:Bayer objects|Draconis, Phi]] [[Category:Flamsteed objects|Draconis, 43]] [[Category:Henry Draper Catalogue objects|170000]] [[Category:Stars with proper names|Zhùshǐ]] [[Category:Astronomy in China|柱史]] [[Category:Hipparcos objects|089908]] [[Category:Bright Star Catalogue objects|6920]] [[Category:Durchmusterung objects]] [[Category:Alpha2 Canum Venaticorum variables]] [[Category:B-type main-sequence stars]] [[Category:Binary stars]]