View source for HAT-P-26

{{Short description|Star in the constellation Virgo}}
{{Starbox begin
| name = HAT-P-26 / Guahayona
}}
{{Starbox observe
| epoch = J2000
| constell = [[Virgo (constellation)|Virgo]]
| ra = {{RA|14|12|37.53311}}<ref name="GaiaDR3"/>
| dec = {{DEC|+04|03|36.1166}}<ref name="GaiaDR3"/>
| appmag_v = 11.76<ref name=simbad/>
}}
{{Starbox character
| type  = [[Main sequence]]
| class = K1V<ref name=Hartman2010/>
}}
{{Starbox astrometry
| radial_v = {{val|14.10|0.39}}<ref name="GaiaDR3"/>
| prop_mo_ra = 37.735
| prop_mo_dec = -142.816
| pm_footnote = <ref name="GaiaDR3"/>
| parallax = 6.9985
| p_error = 0.0204
| parallax_footnote = <ref name="GaiaDR3"/>
}}
{{Starbox detail
| source = <ref name=Hartman2010/>
| mass = {{val|0.816|0.033}}
| radius = {{val|0.788|0.098|0.043}}
| luminosity = {{val|0.38|0.16|0.06}}
| gravity = {{val|4.56|0.06}}
| temperature = {{val|5079|88}}
| metal = {{val|−0.04|0.08}}
| rotational_velocity = {{val|1.8|0.5}}
| age_gyr = {{val|9.0|3.0|4.9}}
}}
{{Starbox catalog
| names = {{odlist | name = Guahayona | GSC=0320-01027 | 2MASS=J14123753+0403359 | TYC=320-1027-1 | Gaia DR2=3668036348641580288}}<ref name=simbad/>
}}
{{Starbox reference
| Simbad = HAT-P-26
}}
{{Starbox end}}

'''HAT-P-26''' is a [[K-type main-sequence star]] located about {{convert|466|ly|pc|lk=on|abbr=off}} away in the [[constellation]] of [[Virgo (constellation)|Virgo]]. A survey in 2015 did not find any stellar companions in orbit around it,<ref>{{citation|arxiv=1507.01938|title=A Lucky Imaging search for stellar companions to transiting planet host stars|year=2015|doi=10.1051/0004-6361/201424091|last1=Wöllert|first1=Maria|last2=Brandner|first2=Wolfgang|last3=Bergfors|first3=Carolina|last4=Henning|first4=Thomas|journal=Astronomy & Astrophysics|volume=575|pages=A23|bibcode=2015A&A...575A..23W |s2cid=119250579}}</ref> although a [[red dwarf]] companion with a temperature {{val|4000|100|350|ul= K}} is suspected on wide orbit.<ref>{{citation|arxiv=1510.08062|year=2015|doi=10.1088/0004-637X/814/2/148|last1=Piskorz|first1=Danielle|last2=Knutson|first2=Heather A.|last3=Ngo|first3=Henry|last4=Muirhead|first4=Philip S.|last5=Batygin|first5=Konstantin|last6=Crepp|first6=Justin R.|last7=Hinkley|first7=Sasha|last8=Morton|first8=Timothy D.|title=Friends of Hot Jupiters. III. An Infrared Spectroscopic Search for Low-Mass Stellar Companions|journal=The Astrophysical Journal|volume=814|issue=2|page=148|bibcode=2015ApJ...814..148P |s2cid=11525988}}</ref>

==Nomenclature==
The designation ''HAT-P-26'' indicates that this was the 26th star found to have a planet by the [[HATNet Project]].

In August 2022, this planetary system was included among 20 systems to be named by the third [[NameExoWorlds]] project.<ref>{{cite web |url=https://www.nameexoworlds.iau.org/2022exoworlds |title=List of ExoWorlds 2022 |date=8 August 2022 |website=nameexoworlds.iau.org |publisher=[[International Astronomical Union|IAU]] |access-date=27 August 2022}}</ref> The approved names, proposed by a team from [[Puerto Rico]], were announced in June 2023. HAT-P-26 is named '''Guahayona''' and its planet is named '''Guataubá''', after figures from [[Taíno]] mythology.<ref name="NEW2022"/>

==Planetary system==
In 2010 a [[Transit (astronomy)|transiting]] [[hot Neptune]] planet was detected.<ref name=Hartman2010/> The transiting planet HAT-P-26b was detected by the [[HATNet Project]] using telescopes located in Hawaii and Arizona. The planet is likely formed by pebble accretion mechanism.<ref>[https://academic.oup.com/mnras/article-abstract/473/1/1325/4159377?redirectedFrom=fulltext Mohamad Ali-Dib, Gunjan Lakhlani, "Possible formation pathways for the low-density Neptune-mass planet HAT-P-26b"]</ref>
The transmission spectrum of HAT-P-26b was taken in 2015, with the best fit favouring either a cloudless atmosphere or an atmosphere with a low-lying cloud deck.<ref>{{citation|arxiv=1511.08226|title=A SEARCH FOR WATER IN THE ATMOSPHERE OF HAT-P-26b USING LDSS-3C|year=2015|doi=10.3847/0004-637X/817/2/141|last1=Stevenson|first1=Kevin B.|last2=Bean|first2=Jacob L.|last3=Seifahrt|first3=Andreas|last4=Gilbert|first4=Gregory J.|last5=Line|first5=Michael R.|last6=Désert|first6=Jean-Michel|last7=Fortney|first7=Jonathan J.|journal=The Astrophysical Journal|volume=817|issue=2|page=141|s2cid=118394486 |doi-access=free }}</ref> The atmospheric composition of the planet was measured in 2019, and a water vapor volume fraction of 1.5{{±|2.1|0.9}}% was detected. HAT-P-26 is carbon depleted, with a C/O ratio constrained to less than 0.33. Also, the planet's atmosphere contains light metal hydrides.<ref>{{citation|arxiv=1903.09151|title=The Metal-Rich Atmosphere of the Neptune HAT-P-26b|year=2019|doi=10.1093/mnras/stz789|last1=MacDonald|first1=Ryan J.|last2=Madhusudhan|first2=Nikku|journal=Monthly Notices of the Royal Astronomical Society|volume=486|pages=1292–1315|doi-access=free |s2cid=85459516}}</ref> The measured planetary temperature is equal to 563{{±|58|54}} [[Kelvin|K]].

In 2023, the atmosphere of the planet was found to contain {{val|2.4|2.9|1.6|u=%}} [[water vapor]] at a temperature of {{val|590|60|50|ul=K}}.<ref name="A-thano2023"/>

A 2019 study detected [[transit-timing variation]]s (TTVs) of HAT-P-26b, the cause of which was unclear at that time.<ref name=Essen2019/> With more data by 2023, it was suggested that the TTVs may be caused by a second planet in the system.<ref name="A-thano2023"/> In 2024, a candidate second planet, about twice the size of Earth and slightly farther from the star than planet b, was detected by transit in [[Transiting Exoplanet Survey Satellite|TESS]] data, but requires further observations to be fully confirmed.<ref name="Dévora-Pajares2024"/>

{{OrbitboxPlanet begin
| table_ref = <ref name=Hartman2010/><ref name="Dévora-Pajares2024"/>
}}
{{OrbitboxPlanet
| exoplanet = b / Guataubá
| mass = {{val|0.059|0.007}}
| radius = {{val|0.565|0.072|0.032}}
| semimajor = {{val|0.0479|0.0006}}
| period = {{val|4.234516|(15)}}
| eccentricity = {{val|0.124|0.060}}
| inclination = {{val|88.6|0.5|0.9}}
}}
{{OrbitboxPlanet hypothetical
| exoplanet = c
| mass_earth = {{val|4.8|3.5|2.0}}{{efn|This mass is predicted based on mass-radius relationships. If this planet is responsible for the observed TTVs it should be possible to measure its mass that way; the 2023 TTV study found a mass of about 6.36 Earths based on an assumed period of 8.47 days,<ref name="A-thano2023"/> but if the period is actually shorter at 6.59 days the mass would be different.}}
| radius_earth = {{val|1.97|0.20}}
| semimajor = 
| period = {{val|6.594|0.009|0.007}}
| eccentricity = <0.09
| inclination = 
}}
{{Orbitbox end}}

==Notes==
{{notelist}}

==References==
{{Reflist|refs=

<ref name="GaiaDR3">{{Cite Gaia DR3|3668036348641580288}}</ref>

<ref name=simbad>[http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HAT-P-26 HAT-P-26 -- High proper-motion Star]</ref>

<ref name=Hartman2010>{{citation|arxiv=1010.1008|title=HAT-P-26b: A LOW-DENSITY NEPTUNE-MASS PLANET TRANSITING A K STAR|year=2010|doi=10.1088/0004-637X/728/2/138|last1=Hartman|first1=J. D.|last2=Bakos|first2=G. Á.|last3=Kipping|first3=D. M.|last4=Torres|first4=G.|last5=Kovács|first5=G.|last6=Noyes|first6=R. W.|last7=Latham|first7=D. W.|last8=Howard|first8=A. W.|last9=Fischer|first9=D. A.|last10=Johnson|first10=J. A.|last11=Marcy|first11=G. W.|last12=Isaacson|first12=H.|last13=Quinn|first13=S. N.|last14=Buchhave|first14=L. A.|last15=Béky|first15=B.|last16=Sasselov|first16=D. D.|last17=Stefanik|first17=R. P.|last18=Esquerdo|first18=G. A.|last19=Everett|first19=M.|last20=Perumpilly|first20=G.|last21=Lázár|first21=J.|last22=Papp|first22=I.|last23=Sári|first23=P.|journal=The Astrophysical Journal|volume=728|issue=2|page=138|s2cid=119228956 |bibcode=2011ApJ...728..138H}}</ref>

<ref name=Essen2019>{{citation|arxiv=1904.06360|title=Indications for transit timing variations in the exo-Neptune HAT-P-26b|year=2019|doi=10.1051/0004-6361/201731966|last1=von Essen|first1=C.|last2=Wedemeyer|first2=S.|last3=Sosa|first3=M. S.|last4=Hjorth|first4=M.|last5=Parkash|first5=V.|last6=Freudenthal|first6=J.|last7=Mallonn|first7=M.|last8=Miculán|first8=R. G.|last9=Zibecchi|first9=L.|last10=Cellone|first10=S.|last11=Torres|first11=A. F.|journal=Astronomy & Astrophysics|volume=628|pages=A116|bibcode=2019A&A...628A.116V |s2cid=118674293}}</ref>

<ref name="NEW2022">{{cite web |url=https://www.nameexoworlds.iau.org/2022approved-names |title=2022 Approved Names |website=nameexoworlds.iau.org |publisher=[[International Astronomical Union|IAU]] |access-date=7 June 2023}}</ref>

<ref name="A-thano2023">{{citation|arxiv=2303.03610|year=2023|title=Revisiting the Transit Timing and Atmosphere Characterization of the Neptune-mass Planet HAT-P-26 b |last1=A-thano |first1=Napaporn |last2=Awiphan |first2=Supachai |last3=Jiang |first3=Ing-Guey |last4=Kerins |first4=Eamonn |last5=Priyadarshi |first5=Akshay |last6=McDonald |first6=Iain |last7=Joshi |first7=Yogesh C. |last8=Chulikorn |first8=Thansuda |last9=Hayes |first9=Joshua J. C. |last10=Charles |first10=Stephen |last11=Huang |first11=Chung-Kai |last12=Rattanamala |first12=Ronnakrit |last13=Yeh |first13=Li-Chin |author14=Vik S Dhillon |journal=The Astronomical Journal |volume=166 |issue=6 |page=223 |doi=10.3847/1538-3881/acfeea |bibcode=2023AJ....166..223A |doi-access=free }}</ref>

<ref name="Dévora-Pajares2024">{{cite journal |last1=Dévora-Pajares |first1=Martín |last2=Pozuelos |first2=Francisco J. |display-authors=etal |date=July 2024 |title=The SHERLOCK pipeline: new exoplanet candidates in the WASP-16, HAT-P-27, HAT-P-26, and TOI-2411 systems |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume= |issue= |pages= |doi=10.1093/mnras/stae1740 |doi-access=free |arxiv=2407.14602}}</ref>

}}

{{Sky|14|12|37.5330|+|04|03|36.1177}}

{{Stars of Virgo}}

[[Category:Virgo (constellation)]]
[[Category:K-type main-sequence stars]]
[[Category:Planetary systems with one confirmed planet]]
[[Category:Planetary transit variables]]
[[Category:Stars with proper names|Guahayona]]