HAT-P-26

HAT-P-26 is a K-type main-sequence star about 302 light-years away. Survey in 2015 did not find any stellar companions on orbit around it,[4] although a red dwarf companion with a temperature 4000+100
−350 K is suspected on wide orbit.[5]

HAT-P-26
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 14h 12m 37.5330s[1]
Declination +04° 03′ 36.1177″[1]
Apparent magnitude (V) 11.76[1]
Characteristics
Spectral type K1V
Astrometry
Parallax (π)10.7960 ± 0.0561[1] mas
Distance302 ± 2 ly
(92.6 ± 0.5 pc)
Details[2]
Mass0.81 M☉
Radius0.78 R☉
Temperature5079±88 K
Metallicity-0.04±0.08[3]
Rotational velocity (v sin i)1.8 km/s
Other designations
Gaia DR2 3668036348641580288, TYC 320-1027-1, GSC 0320-01027, 2MASS J14123753+0403359[1]
Database references
SIMBADdata

Planetary system

In 2010 a transiting hot Neptune like planet was detected.[3] 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.[6] The transmission spectrum of the HAT-P-26b was taken in the 2015, with best fit favouring either cloudless atmosphere or atmosphere with low-lying cloud deck.[7] The atmospheric composition of the planet was measured in 2019, and the water vapor volume fraction of 1.5+2.1
−0.9% was detected. The HAT-P-26 is carbon depleted, C/O ratio been constrained to less than 0.33. Also, atmosphere contains light metal hydrides.[8] The measured planetary temperature is equal to 563+58
−54 K.

In 2019, the transit timing variation analysis of HAT-P-26b, has indicated a presence of the second planet in the system on the wide, 1141-days orbit.[9]

The HAT-P-26 planetary system[10][9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b >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. HAT-P-26 -- High proper-motion Star
  2. D. Ehrenreich and J.-M. Désert, "Mass-loss rates for transiting exoplanets", A&A 529, A136 (2011)
  3. 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
  4. 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, doi:10.1051/0004-6361/201424091, S2CID 119250579
  5. 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, doi:10.1088/0004-637X/814/2/148, S2CID 11525988
  6. Mohamad Ali-Dib, Gunjan Lakhlani, "Possible formation pathways for the low-density Neptune-mass planet HAT-P-26b"
  7. 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
  8. 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
  9. 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, doi:10.1051/0004-6361/201731966, S2CID 118674293
  10. Planet HAT-P-26 b on exoplanet.eu


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