{{Short description|Star in the constellation of Ara}} {{Starbox begin}} {{Starbox observe | epoch = J2000 | constell = Ara<ref name=Anderson_Francis_2012/> | ra = {{RA|17|11|15.72205}}<ref name=GaiaDR3/> | dec = {{DEC|−56|40|50.8712}}<ref name=GaiaDR3/> | appmag_v = 7.25<ref name=Anderson_Francis_2012/> }} {{Starbox character | type = subgiant<ref name=GaiaDR3/> | class = G5IV-V<ref name="McCarthy2004"/> | b-v = {{val|0.699|0.001}}<ref name=Anderson_Francis_2012/> | u-b = | variable = Constant<ref name=Bonfanti_et_al_2016/> }} {{Starbox astrometry | radial_v = {{val|+28.10|0.12}}<ref name=GaiaDR3/> | prop_mo_ra = +87.442<ref name=GaiaDR3/> | prop_mo_dec = −55.861<ref name=GaiaDR3/> | parallax = 15.8176 | p_error = 0.0197 | parallax_footnote = <ref name=GaiaDR3/> | absmag_v = 3.07<ref name="McCarthy2004"/> }} {{Starbox detail | mass = {{val|1.718|0.03|0.022}}<ref name="Wittenmyer"/> | radius = {{val|2.1|0.1}}<ref name=Bonfanti_et_al_2016/> | luminosity = {{val|4.4|0.3}}<ref name=Bonfanti_et_al_2016/> | temperature = {{val|5740|46|fmt=commas}}<ref name=Bonfanti_et_al_2016/> | metal_fe = {{val|−0.26|0.01}}<ref name=Sousa_et_al_2018/> | rotational_velocity = {{val|1.44|0.50}}<ref name=Butler_et_al_2006/> | gravity = {{val|3.83|0.03}}<ref name=Bonfanti_et_al_2016/> | age_gyr = {{val|5.8|0.5}}<ref name=Bonfanti_et_al_2016/> }} {{Starbox catalog | names = {{odlist | CD=−56°6717 | CPC=20 5475 | CPD=−56°8059 | GC=23146 | GSC=08735-01682 | HD=154857 | HIP=84069 | PPM=345752 | SAO=244491 | TYC=8735-1682-1 }}<ref name=SIMBAD/> }} {{Starbox reference | Simbad = HD+154857 | ARICNS = }} {{Starbox end}}
'''HD 154857''' is a star with two exoplanetary companions in the southern constellation of Ara. It is too dim to be visible with the naked eye having an apparent visual magnitude of 7.25.<ref name=Anderson_Francis_2012/> The star is located at a distance of 206 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +28 km/s.<ref name=GaiaDR3/>
This is a G-type star with a stellar classification of G5IV-V.<ref name="McCarthy2004"/> The absolute magnitude of this star is two magnitudes above the main sequence, which suggests that the star is evolving toward the subgiant stage.<ref name="McCarthy2004"/> It is a metal-poor thin disk star<ref name=Gonzalez2009/> approximately six billion years old and is chromopherically quiet although not in a Maunder Minimum state.<ref name=Bonfanti_et_al_2016/> The star is larger, more massive, and more luminous than the Sun. It is spinning with a projected rotational velocity of 1.4 km/s.<ref name=Butler_et_al_2006/>
==Planetary system==
The discovery of one confirmed and one unconfirmed Jovian exoplanet was reported in 2004<ref name="McCarthy2004"/> and 2007<ref name="O'Toole2007"/> respectively. The former planet HD 154857 b has mass >1.8 times that of Jupiter. It orbits the star 20% further than Earth-Sun distance, taking 409 days with 47% eccentricity. The additional object (HD 154857 c) was confirmed as a planetary companion in January 2014.<ref name="Wittenmyer"/>
{{OrbitboxPlanet begin | table_ref = <ref name="Wittenmyer" /> }} {{OrbitboxPlanet | exoplanet = b | mass = {{val|2.24|0.05|p=≥ }} | period = {{val|408.6|0.5}} | semimajor = {{val|1.291|0.008}} | eccentricity = {{val|0.06|0.05}} }} {{OrbitboxPlanet | exoplanet = c | mass = {{val|2.58|0.16|p=≥ }} | period = {{val|3452|105|fmt=commas}} | semimajor = {{val|5.36|0.09}} | eccentricity = {{val|0.06|0.05}} }} {{Orbitbox end}}
==See also==
==References== {{Reflist|colwidth=30em|refs=
<ref name=SIMBAD>{{cite simbad | title=HD 154857 | access-date=2021-10-10 }}</ref>
<ref name=GaiaDR3>{{Cite Gaia DR3|5917212800626605824}}</ref>
<ref name=Anderson_Francis_2012>{{cite XHIP|84069}}</ref>
<ref name="McCarthy2004">{{cite journal | title=Multiple Companions to HD 154857 and HD 160691 | last1=McCarthy | first1=Chris | last2=Butler | first2=R. Paul | last3=Tinney | first3=C. G. | last4=Jones | first4=Hugh R. A. | last5=Marcy | first5=Geoffrey W. | last6=Carter | first6=Brad | last7=Penny | first7=Alan J. | last8=Fischer | first8=Debra A. | display-authors=1 | journal=The Astrophysical Journal | volume=617 | issue=1 | pages=575–579 | date=2004 | arxiv=astro-ph/0409335 | bibcode=2004ApJ...617..575M | doi=10.1086/425214 | s2cid=119446133 }}</ref>
<ref name="O'Toole2007">{{cite journal | title=New Planets around Three G Dwarfs | last1=O'Toole | first1=Simon J. | last2=Butler | first2=R. Paul | last3=Tinney | first3=C. G. | last4=Jones | first4=Hugh R. A. | last5=Marcy | first5=Geoffrey W. | last6=Carter | first6=Brad | last7=McCarthy | first7=Chris | last8=Bailey | first8=Jeremy | last9=Penny | first9=Alan J. | display-authors=1 | journal=The Astrophysical Journal | volume=660 | issue=2 | pages=1636–1641 | date=2007 | arxiv=astro-ph/0702213 | bibcode=2007ApJ...660.1636O | doi=10.1086/513563 | s2cid=118958847 }}</ref>
<ref name="Wittenmyer">{{cite journal | title=The Anglo-Australian Planet Search. XXIII. Two New Jupiter Analogs | first1=Robert A. | last1=Wittenmyer | first2=Jonathan | last2=Horner | first3=C. G. | last3=Tinney | first4=R. P. | last4=Butler | first5=H. R. A. | last5=Jones | first6=Mikko | last6=Tuomi | first7=G. S. | last7=Salter | first8=B. D. | last8=Carter | first9=F. Elliott | last9=Koch | first10=S. J. | last10=O'Toole | first11=J. | last11=Bailey | first12=D. | last12=Wright | display-authors=1 | journal=The Astrophysical Journal | volume=783 | issue=2 | id=103 | pages=9 | date=March 2014 | doi=10.1088/0004-637X/783/2/103 | arxiv=1401.5525 | bibcode=2014ApJ...783..103W | s2cid=14082923 }}</ref>
<ref name=Sousa_et_al_2018>{{cite journal | title=SWEET-Cat updated. New homogenous spectroscopic parameters | display-authors=1 | last1=Sousa | first1=S. G. | last2=Adibekyan | first2=V. | last3=Delgado-Mena | first3=E. | last4=Santos | first4=N. C. | last5=Andreasen | first5=D. T. | last6=Ferreira | first6=A. C. S. | last7=Tsantaki | first7=M. | last8=Barros | first8=S. C. C. | last9=Demangeon | first9=O. | last10=Israelian | first10=G. | last11=Faria | first11=J. P. | last12=Figueira | first12=P. | last13=Mortier | first13=A. | last14=Brandão | first14=I. | last15=Montalto | first15=M. | last16=Rojas-Ayala | first16=B. | last17=Santerne | first17=A. | journal=Astronomy & Astrophysics | volume=620 | id=A58 | pages=13 | date=November 2018 | doi=10.1051/0004-6361/201833350 | arxiv=1810.08108 | bibcode=2018A&A...620A..58S | s2cid=119374557 }}</ref>
<ref name=Bonfanti_et_al_2016>{{cite journal | title=Age consistency between exoplanet hosts and field stars | last1=Bonfanti | first1=A. | last2=Ortolani | first2=S. | last3=Nascimbeni | first3=V. | journal=Astronomy & Astrophysics | year=2016 | volume=585 | id=A5 | pages=14 | arxiv=1511.01744 | bibcode=2016A&A...585A...5B | doi=10.1051/0004-6361/201527297 | s2cid=53971692 }}</ref>
<ref name=Butler_et_al_2006>{{cite journal | last1=Butler | first1=R. P. | last2=Wright | first2=J. T. | last3=Marcy | first3=G. W. | last4=Fischer | first4=D. A. | last5=Vogt | first5=S. S. | last6=Tinney | first6=C. G. | last7=Jones | first7=H. R. A. | last8=Carter | first8=B. D. | last9=Johnson | first9=J. A. | display-authors=1 | title=Catalog of Nearby Exoplanets | journal=The Astrophysical Journal | volume=646 | issue=1 | pages=505–522 | date=December 2006 | doi=10.1086/504701 | arxiv=astro-ph/0607493 | bibcode=2006ApJ...646..505B | s2cid=119067572 }}</ref>
<ref name=Gonzalez2009>{{cite journal | title=Stars with planets and the thick disc | last=Gonzalez | first=Guillermo | journal=Monthly Notices of the Royal Astronomical Society: Letters | volume=399 | issue=1 | pages=L103–L107 | date=October 2009 | doi=10.1111/j.1745-3933.2009.00734.x | bibcode=2009MNRAS.399L.103G | doi-access=free }}</ref>
}}
==External links== * {{cite encyclopedia|url=http://exoplanet.eu/star.php?st=HD+154857|archive-url=https://web.archive.org/web/20070702190615/http://exoplanet.eu/star.php?st=HD+154857|url-status=dead|archive-date=July 2, 2007|encyclopedia=Extrasolar Planets Encyclopaedia|title=HD 154857|access-date=2008-07-21}} * [https://web.archive.org/web/20080916061358/http://planetquest.jpl.nasa.gov/atlas/atlas_profile.cfm?Planet=261 http://planetquest.jpl.nasa.gov]
{{Sky|17|11|15.7219|-|56|40|50.865|223.55}} {{Stars of Ara}}
{{DEFAULTSORT:HD 154857}} <!-- Properties --> Category:G-type subgiants Category:Planetary systems with two confirmed planets <!-- Other --> Category:Ara (constellation) Category:Durchmusterung objects 154857 084069