{{Short description|Star in the constellation Boötes}} {{Starbox begin}} {{Starbox image | image = [[Image:HNBooLightCurve.png|250px]] | caption = A [[Photometric_system#Photometric_letters|near infrared (Y band)]] [[light curve]] for HN Boötes, adapted from Strassmeier ''et al.'' (2000)<ref name="Strassmeier"/> }} {{Starbox observe | epoch = J2000 | constell = [[Boötes]] | ra = {{RA|14|36|00.56073}}<ref name=GaiaDR2/> | dec = {{DEC|+09|44|47.4536}}<ref name=GaiaDR2/> | appmag_v = 7.48<ref name=Anderson_Francis_2012/> }} {{Starbox character | type = | class = K3V<ref name=Koen_et_al_2010/> | b-v = {{val|0.973|0.004}}<ref name=Anderson_Francis_2012/> | u-b = | variable = [[BY Draconis variable|BY Dra]]<ref name=gcvs/> }} {{Starbox astrometry | radial_v = {{val|−9.62|0.15}}<ref name=GaiaDR2/> | prop_mo_ra = 204.360<ref name=GaiaDR2/> | prop_mo_dec = −250.390<ref name=GaiaDR2/> | parallax = 61.2111 | p_error = 0.0740 | parallax_footnote = <ref name=GaiaDR2/> | absmag_v = 6.39<ref name=Anderson_Francis_2012/> }} {{Starbox detail | source = | mass = 0.82<ref name=Luck2017/> | radius = {{val|0.78|0.01}}<ref name=GaiaDR2/> | luminosity = {{val|0.308|0.001}}<ref name=GaiaDR2/> | temperature = {{val|4863|46|15|fmt=commas}}<ref name=GaiaDR2/> | metal_fe = 0.08<ref name="Rein2009"/> dex<br>0.12<ref name=Luck2017/> | gravity = 4.58<ref name=Luck2017/> | rotational_velocity = 5.6<ref name=Luck2017/> | age_gyr = 0.5–1.0 Gyr<ref name="Vogt2005"/><br>6.35<ref name=Luck2017/> }} {{Starbox catalog | names = {{odlist | BD=+10°2710 | GC=19679 | GJ=3860 | GSC=00910-00165 | HD=128311 | HIP=71395 | V=HN Boo | LTT=14312 | SAO=120554 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = HD+128311 | ARICNS = 04323 }} {{Starbox end}}
'''HD 128311''' is a [[variable star]] in the northern [[constellation]] of [[Boötes]]. It has the [[variable star designation]] '''HN Boötis''', while HD 128311 is the star's designation in the ''[[Henry Draper Catalogue]]''. The star is invisible to the [[naked eye]] with an [[apparent visual magnitude]] that fluctuates around 7.48.<ref name=Anderson_Francis_2012/> It is located at a distance of 53 [[light year]]s from the [[Sun]] based on [[stellar parallax|parallax]], but is drifting closer with a [[radial velocity]] of −9.6 km/s.<ref name=GaiaDR2/> Two confirmed [[extrasolar planet]]s have been detected in orbit around this star.<ref name="Vogt2005"/>
The [[stellar classification]] of HN Boo is K3V,<ref name=Koen_et_al_2010/> which indicates this is a [[K-type main sequence star]]. Klaus G. Strassmeier ''et al.'' announced that the star's brightness varies, in the year 2000.<ref name="Strassmeier"/> It was given its variable star designation in 2006.<ref name="Kazarovets2006"/> It is a [[BY Draconis variable|BY Draconis-type variable]], randomly varying in brightness by 0.04 in magnitude over a period of 11.54 days<ref name=gcvs/> due to [[star spot]]s and high [[chromospheric activity]]. The star exhibits strong emission, which suggests an age of 0.5–1.0 billion years.<ref name="Vogt2005"/> It has 82% of the [[mass of the Sun]] and 78% of the [[Sun's radius]]. The [[metallicity]] of the star, meaning its abundance of heavier elements, appears slightly higher than in the Sun. It is radiating 31% of the [[luminosity of the Sun]] from its [[photosphere]] at an [[effective temperature]] of 4,863 K.<ref name=Luck2017/>
== Planetary system ==
{{OrbitboxPlanet begin | table_ref = }} {{OrbitboxPlanet hypothetical | exoplanet = d | mass = ≥{{val|0.133|0.005}}<ref name="McArthur2014"/> | period = {{val|11.2210|0.0008}}<ref name="McArthur2014"/> | semimajor = {{val|0.092|0.004}}<ref name="McArthur2014"/> | eccentricity = {{val|0.196|0.030}}<ref name="McArthur2014"/> }} {{OrbitboxPlanet | exoplanet = [[HD 128311 b|b]] | mass = {{val|1.9|0.7|0.3}}<ref name="Van Zandt 2026"/> | period = {{val|453.019|0.404}}<ref name="McArthur2014"/> | semimajor = {{val|1.09|0.01}}<ref name="Van Zandt 2026"/> | eccentricity = {{val|0.30|0.04}}<ref name="Van Zandt 2026"/> | inclination = {{val|90|30|40}}<ref name="Van Zandt 2026"/> }} {{OrbitboxPlanet | exoplanet = [[HD 128311 c|c]] | mass = {{val|3.4|0.6|0.2}}<ref name="Van Zandt 2026"/> | period = {{val|921.538|1.15}}<ref name="McArthur2014"/> | semimajor = {{val|1.75|0.02}}<ref name="Van Zandt 2026"/> | eccentricity = {{val|0.19|0.05|0.07}}<ref name="Van Zandt 2026"/> | inclination = {{Val|70|40|20}}<ref name="Van Zandt 2026"/> }} {{Orbitbox end}}
In 2002, the discovery of the [[exoplanet]] [[HD 128311 b]] was announced by [[R. Paul Butler|Paul Butler]].<ref name="Butler2003"/> In 2005, the discovery of a second exoplanet [[HD 128311 c]] was announced by [[Steven S. Vogt|Steve Vogt]].<ref name="Vogt2005"/>
Most likely, the system has been formed in a very turbulent disc.<ref name="Rein2009"/> The authors were able to show with both analytic and numerical models that certain libration modes are readily excited by turbulence. It was initially thought that the system could have been resulted from planet–planet scattering, but this is rather unlikely.
In 2014, the true mass of HD 128311 c was measured via [[astrometry]]. The same study also proposed a third planetary candidate, but it has not been confirmed.<ref name="McArthur2014"/> In 2026, the mass of HD 128311 b was also measured with astrometry.<ref name="Van Zandt 2026"/><!-- The designations in the paper are swapped, so 'HD 128311 b' in the paper refers actually to 'HD 128311 c' in other papers. -->
[[Image:Hd128311.png|thumb|500px|none|alt=Time evolution of orbital elements in the system HD128311. This left panel in this plot shows the most likely formation scenario for the planetary system. The right panel shows the observed orbital configuration.|Time evolution of orbital elements in the system HD128311. This left panel in this plot shows the most likely formation scenario for the planetary system. The right panel shows the observed orbital configuration.]]
==References== {{Reflist|colwidth=30em|refs=
<ref name="Strassmeier">{{cite journal |last1=Strassmeier |first1=K. G. |last2=Washuettl |first2=A. |last3=Granzer |first3=Th. |last4=Scheck |first4=M. |last5=Weber |first5=M. |title=The Vienna-KPNO search for Doppler-imaging candidate stars |journal=Astronomy & Astrophysics Supplement Series |date=March 2000 |volume=142 |issue=2 |pages=275–311 |doi=10.1051/aas:2000328 |bibcode=2000A&AS..142..275S |doi-access=free }}</ref>
<ref name=SIMBAD>{{cite simbad | title=HD 128311 | access-date=2021-04-06 }}</ref>
<ref name=GaiaDR2>{{Cite Gaia DR2|1176209886733406592}}</ref>
<ref name="Kazarovets2006">{{cite journal | last1=Kazarovets | first1=E. V. | last2=Samus | first2=N. N. | last3=Durlevich | first3=O. V. | last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N. | title=The 78th Name-List of Variable Stars | journal=Information Bulletin on Variable Stars | date=August 2006 | volume=5721 | pages=1–45 | bibcode=2006IBVS.5721....1K | url=https://ibvs.konkoly.hu/pub/ibvs/5701/5721.pdf | access-date=6 December 2024}}</ref>
<ref name=gcvs>{{cite journal | title=General catalogue of variable stars: Version GCVS 5.1 | last1=Samus' | first1=N. N | last2=Kazarovets | first2=E. V | last3=Durlevich | first3=O. V | last4=Kireeva | first4=N. N | last5=Pastukhova | first5=E. N | journal=Astronomy Reports | volume=61 | issue=1 | pages=80 | year=2017 | doi=10.1134/S1063772917010085 | bibcode=2017ARep...61...80S | s2cid=125853869 }}</ref>
<ref name=Luck2017>{{cite journal | title=Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants | last=Luck | first=R. Earle | journal=The Astronomical Journal | volume=153 | issue=1 | id=21 | pages=19 | date=January 2017 | bibcode=2017AJ....153...21L | arxiv=1611.02897 | doi=10.3847/1538-3881/153/1/21 | s2cid=119511744 | doi-access=free }}</ref>
<ref name=Anderson_Francis_2012>{{cite journal | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | bibcode=2012AstL...38..331A | arxiv=1108.4971 | doi=10.1134/S1063773712050015 | s2cid=119257644 }}</ref>
<ref name=Koen_et_al_2010>{{cite journal | title=UBV(RI)<sub>C</sub>JHK observations of Hipparcos-selected nearby stars | last1=Koen | first1=C. | last2=Kilkenny | first2=D. | last3=van Wyk | first3=F. | last4=Marang | first4=F. | display-authors=1 | journal=Monthly Notices of the Royal Astronomical Society | volume=403 | issue=4 | date=April 21, 2010 | pages=1949–1968 | doi=10.1111/j.1365-2966.2009.16182.x | bibcode=2010MNRAS.403.1949K | doi-access=free }}</ref>
<ref name="Van Zandt 2026">{{Cite journal |last1=Van Zandt |first1=Judah |last2=Gilbert |first2=Gregory J. |last3=Petigura |first3=Erik A. |last4=Giacalone |first4=Steven |last5=Howard |first5=Andrew W. |last6=Handley |first6=Luke B. |date=2026-04-02 |title=A Smooth Transition from Giant Planets to Brown Dwarfs from the Radial Occurrence Distribution |journal=The Astronomical Journal |volume=171 |issue=5 |pages=267 |doi=10.3847/1538-3881/ae5102 |doi-access=free |issn=0004-6256}}</ref>
<ref name="Butler2003">{{cite journal | title=Seven New Keck Planets Orbiting G and K Dwarfs | last1=Butler | first1=R. Paul | last2=Marcy | first2=Geoffrey W. | last3=Vogt | first3=Steven S. | last4=Fischer | first4=Debra A. | last5=Henry | first5=Gregory W. | last6=Laughlin | first6=Gregory | last7=Wright | first7=Jason T. | display-authors=1 | journal=The Astrophysical Journal | volume=582 | issue=1 | pages=455–466 | date=2003 | doi=10.1086/344570 | bibcode=2003ApJ...582..455B | citeseerx=10.1.1.7.6988 | s2cid=17608922 }}</ref>
<ref name="Rein2009">{{cite journal | title=On the evolution of mean motion resonances through stochastic forcing: Fast and slow libration modes and the origin of HD128311 | last1=Rein | first1=Hanno | last2=Papaloizou | first2=J. C. B. | journal= Astronomy and Astrophysics | date=2009 | volume=497 | issue=2 | pages=595–609 | arxiv=0811.1813 | doi=10.1051/0004-6361/200811330 | bibcode=2009A&A...497..595R| s2cid=12286814 }}</ref>
<ref name="Vogt2005">{{cite journal | title=Five New Multicomponent Planetary Systems | last1=Vogt | first1=Steven S. | last2=Butler | first2=R. Paul | last3=Marcy | first3=Geoffrey W. | last4=Fischer | first4=Debra A. | last5=Henry | first5=Gregory W. | last6=Laughlin | first6=Greg | last7=Wright | first7=Jason T. | last8=Johnson | first8=John A. | display-authors=1 | journal=The Astrophysical Journal | volume=632 | issue=1 | pages=638–658 | date=2005 | doi=10.1086/432901 | bibcode=2005ApJ...632..638V| s2cid=16509245 | url=https://authors.library.caltech.edu/36250/1/0004-637X_632_1_638.pdf }}</ref>
<ref name="McArthur2014">{{cite journal | title=Astrometry, Radial Velocity, and Photometry: The HD 128311 System Remixed with Data from HST, HET, and APT | last1=McArthur | first1=Barbara E. | display-authors=etal | journal=[[The Astrophysical Journal]] | year=2014 | volume=795 | issue=1 | page=41 | doi=10.1088/0004-637X/795/1/41 | bibcode=2014ApJ...795...41M | s2cid=122980723 | doi-access=free | hdl=2152/35199 | hdl-access=free }}</ref>
}}
==External links== * {{cite encyclopedia | url=http://exoplanet.eu/star.php?st=HD+128311 | archive-url=https://web.archive.org/web/20070702185725/http://exoplanet.eu/star.php?st=HD+128311 | url-status=dead | archive-date=July 2, 2007 | encyclopedia=[[Extrasolar Planets Encyclopaedia]] | title=Notes for star HD 128311 | access-date=2008-08-18 }}
==External links== * [http://webviz.u-strasbg.fr/viz-bin/VizieR-S?GJ%203860 GJ 3860] * [http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ Extrasolar Planet Interactions] {{Webarchive|url=https://web.archive.org/web/20160505160348/http://www.lpl.arizona.edu/~rory/research/xsp/dynamics/ |date=2016-05-05 }} by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona * [http://aladin.u-strasbg.fr/AladinPreview?-c=14+36+00.5607%2B09+44+47.466&ident=V*+HN+Boo&submit=Aladin+previewer Image HD 128311] __NOTOC__ {{HD 128311}} {{Stars of Boötes}} {{Sky|14|36|00.5607|+|09|44|47.466|54.14}} <!-- Properties --> [[Category:K-type main-sequence stars]] [[Category:BY Draconis variables]] [[Category:Planetary systems with two confirmed planets]] <!-- Other --> [[Category:Boötes]] [[Category:Durchmusterung objects]] [[Category:Gliese and GJ objects|3860]] [[Category:Henry Draper Catalogue objects|128311]] [[Category:Hipparcos objects|071395]] [[Category:Objects with variable star designations|Boötis, HN]]