HAT-P-26

HAT-P-26 is a K-type main-sequence star about 466 light-years (143 parsecs) away. A survey in 2015 did not find any stellar companions in orbit around it,[5] although a red dwarf companion with a temperature 4000+100
−350 K is suspected on wide orbit.[6]

HAT-P-26 / Guahayona
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 14h 12m 37.53311s[1]
Declination +04° 03′ 36.1166″[1]
Apparent magnitude (V) 11.76[2]
Characteristics
Spectral type K1V
Astrometry
Radial velocity (Rv)14.10±0.39[1] km/s
Proper motion (μ) RA: 37.735 mas/yr[1]
Dec.: -142.816 mas/yr[1]
Parallax (π)6.9985 ± 0.0204 mas[1]
Distance466 ± 1 ly
(142.9 ± 0.4 pc)
Details[3]
Mass0.81 M☉
Radius0.78 R☉
Temperature5079±88 K
Metallicity-0.04±0.08[4]
Rotational velocity (v sin i)1.8 km/s
Other designations
Guahayona, Gaia DR2 3668036348641580288, TYC 320-1027-1, GSC 0320-01027, 2MASS J14123753+0403359[2]
Database references
SIMBADdata

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.[7] 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.[8]

Planetary system

In 2010 a transiting hot Neptune like planet was detected.[4] 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.[9] 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.[10] 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.[11] The measured planetary temperature is equal to 563+58
−54 K.

In 2019, a transit timing variation analysis of HAT-P-26b indicated the possible presence of a second planet in the system on a wide, 1141-days orbit.[12]

In 2023, the atmosphere of the planet was confirmed to contain 12±2 percents of steam at temperature 590+20
−30K.[13]

The HAT-P-26 planetary system[14][12]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b / Guataubá >0.0585±0.00717 MJ 0.0479±0.0006 4.234516±0.000015 0.124±0.060 88.6±0.9° 0.5647±0.0517 RJ
c (unconfirmed) — — 1141 — — —

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. HAT-P-26 -- High proper-motion Star
  3. D. Ehrenreich and J.-M. Désert, "Mass-loss rates for transiting exoplanets", A&A 529, A136 (2011)
  4. Hartman, J. D.; Bakos, G. Á.; Kipping, D. M.; Torres, G.; Kovács, G.; Noyes, R. W.; Latham, D. W.; Howard, A. W.; Fischer, D. A.; Johnson, J. A.; Marcy, G. W.; Isaacson, H.; Quinn, S. N.; Buchhave, L. A.; Béky, B.; Sasselov, D. D.; Stefanik, R. P.; Esquerdo, G. A.; Everett, M.; Perumpilly, G.; Lázár, J.; Papp, I.; Sári, P. (2010), "HAT-P-26b: A LOW-DENSITY NEPTUNE-MASS PLANET TRANSITING A K STAR", The Astrophysical Journal, 728 (2): 138, arXiv:1010.1008, doi:10.1088/0004-637X/728/2/138, S2CID 119228956
  5. Wöllert, Maria; Brandner, Wolfgang; Bergfors, Carolina; Henning, Thomas (2015), "A Lucky Imaging search for stellar companions to transiting planet host stars", Astronomy & Astrophysics, 575: A23, arXiv:1507.01938, Bibcode:2015A&A...575A..23W, doi:10.1051/0004-6361/201424091, S2CID 119250579
  6. Piskorz, Danielle; Knutson, Heather A.; Ngo, Henry; Muirhead, Philip S.; Batygin, Konstantin; Crepp, Justin R.; Hinkley, Sasha; Morton, Timothy D. (2015), "Friends of Hot Jupiters. III. An Infrared Spectroscopic Search for Low-Mass Stellar Companions", The Astrophysical Journal, 814 (2): 148, arXiv:1510.08062, Bibcode:2015ApJ...814..148P, doi:10.1088/0004-637X/814/2/148, S2CID 11525988
  7. "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.
  8. "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
  9. Mohamad Ali-Dib, Gunjan Lakhlani, "Possible formation pathways for the low-density Neptune-mass planet HAT-P-26b"
  10. Stevenson, Kevin B.; Bean, Jacob L.; Seifahrt, Andreas; Gilbert, Gregory J.; Line, Michael R.; Désert, Jean-Michel; Fortney, Jonathan J. (2015), "A SEARCH FOR WATER IN THE ATMOSPHERE OF HAT-P-26b USING LDSS-3C", The Astrophysical Journal, 817 (2): 141, arXiv:1511.08226, doi:10.3847/0004-637X/817/2/141, S2CID 118394486
  11. MacDonald, Ryan J.; Madhusudhan, Nikku (2019), "The Metal-Rich Atmosphere of the Neptune HAT-P-26b", Monthly Notices of the Royal Astronomical Society, 486: 1292–1315, arXiv:1903.09151, doi:10.1093/mnras/stz789, S2CID 85459516
  12. von Essen, C.; Wedemeyer, S.; Sosa, M. S.; Hjorth, M.; Parkash, V.; Freudenthal, J.; Mallonn, M.; Miculán, R. G.; Zibecchi, L.; Cellone, S.; Torres, A. F. (2019), "Indications for transit timing variations in the exo-Neptune HAT-P-26b", Astronomy & Astrophysics, 628: A116, arXiv:1904.06360, Bibcode:2019A&A...628A.116V, doi:10.1051/0004-6361/201731966, S2CID 118674293
  13. Revisiting the Transit Timing and Atmosphere Characterization of the Neptune-mass Planet HAT-P-26 b, 2023, arXiv:2303.03610
  14. Planet HAT-P-26 b on exoplanet.eu
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