KELT-20

KELT-20
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Cygnus
Right ascension 19h 38m 38.735s
Declination +31° 31′ 09.22″
Apparent magnitude (V) 7.58
Characteristics
Evolutionary stage main sequence
Spectral type A2V
Variable type planetary transit
Astrometry
Proper motion (μ) RA: 3.251+0.030
−0.008 mas/yr
Dec.: −6.01±0.03 mas/yr
Parallax (π)7.3015±0.0433 mas
Distance447 ± 3 ly
(137.0 ± 0.8 pc)
Absolute magnitude (MV)+2.30
Orbit
Period (P)12+15
−6 yr
Semi-major axis (a)6.6+4.8
−2.4 au
Eccentricity (e)0.43+0.34
−0.30
Inclination (i)86+57
−52°
Longitude of the node (Ω)63+160
−46°
Argument of periastron (ω)
(secondary)		195±86°
Details
KELT-20
Mass2.3 M☉
Radius1.6 R☉
Luminosity15.7 L☉
Surface gravity (log g)4.38 cgs
Temperature9,032 K
Metallicity [Fe/H]−0.02±0.07 dex
Age58±5 Myr
Brown dwarf
Mass34+29
−11 MJup
Other designations
HD 185603, HIP 96618, MASCARA-2, KELT-20
Database references
SIMBADdata

KELT-20, also known as MASCARA-2, is an A2 main sequence star in the constellation of Cygnus, about 447 light years away.

A brown dwarf companion was found in 2026 with the use of radial velocity and astrometry.

Nomenclature

KELT-20 is the star's KELT designation. It is also designated as MASCARA-2 meaning that it is the second star observed by the MASCARA exoplanet search program. Its Henry Draper Catalogue designation is HD 185603, and its Hipparcos designation is HIP 96618.

Planetary system

In 2017, the discovery of the planet KELT-20b was announced.

The KELT-20 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination
(°)		 Radius
b 3.382 MJ 0.05 3.6127647 — 86.12 1.741 RJ

References

  1. 1 2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. 1 2 3 4 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.
  3. ↑ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862. ISBN 978-0333750889.{{cite journal}}: CS1 maint: periodical has ISBN (link)
  4. ↑ Lund, Michael B.; et al. (2017). "KELT-20b: A Giant Planet with a Period of P ∼ 3.5 days Transiting the V ∼ 7.6 Early a Star HD 185603". The Astronomical Journal. 154 (5): 194. arXiv:1707.01518. Bibcode:2017AJ....154..194L. doi:10.3847/1538-3881/aa8f95.
  5. 1 2 3 4 5 Yang, Eritas; Lu, Tiger; Yahalomi, Daniel A.; Winn, Joshua N. (2026-06-01). "A Massive Hot-Jupiter Companion that Disfavors Giant Planet Formation Beyond the Water-Ice Line". The Astrophysical Journal Letters. arXiv:2606.02705.
  6. 1 2 3 4 5 Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881.
  7. ↑ Talens, G. J. J.; Justesen, A. B.; Albrecht, S.; McCormac, J.; Van Eylen, V.; Otten, G. P. P. L.; Murgas, F.; Palle, E.; Pollacco, D.; Stuik, R.; Spronck, J. F. P.; Lesage, A. -L.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Snellen, I. A. G. (2018). "MASCARA-2 b. A hot Jupiter transiting the mV = 7.6 A-star HD 185603". Astronomy and Astrophysics. 612. arXiv:1707.01500. Bibcode:2018A&A...612A..57T. doi:10.1051/0004-6361/201731512. S2CID 119422884.
  8. ↑ Distler, Adam; Soares-Furtado, Melinda; Mann, Andrew W.; Kraus, Adam L.; Gagné, Jonathan; Becker, Juliette; Narayan, Ritvik Sai; Clark, Max; Vanderburg, Andrew (2026-03-01). "TESS Hunt for Young and Maturing Exoplanets (THYME) XIV: A Comoving-Based Age Constraint for KELT-20". The Astronomical Journal. arXiv:2603.01313.
  9. ↑ Yan, F.; Reiners, A.; Pallé, E.; Shulyak, D.; Stangret, M.; Molaverdikhani, K.; Nortmann, L.; Mollière, P.; Henning, Th.; Casasayas-Barris, N.; Cont, D.; Chen, G.; Czesla, S.; Sánchez-López, A.; López-Puertas, M.; Ribas, I.; Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Galadí-Enríquez, D.; Khalafinejad, S.; Lara, L. M.; Montes, D.; Morello, G.; Nagel, E.; Sedaghati, E.; Zapatero Osorio, M. R.; Zechmeister, M. (2022), "Detection of iron emission lines and a temperature inversion on the dayside of the ultra-hot Jupiter KELT-20b", Astronomy & Astrophysics, 659: A7, arXiv:2201.08759, Bibcode:2022A&A...659A...7Y, doi:10.1051/0004-6361/202142395, S2CID 246210387
  10. ↑ Fu, Guangwei; Sing, David K.; Lothringer, Joshua D.; Deming, Drake; Ih, Jegug; Kempton, Eliza M. -R.; Malik, Matej; Komacek, Thaddeus D.; Mansfield, Megan; Bean, Jacob L. (2022), "Strong H2O and CO Emission Features in the Spectrum of KELT-20b Driven by Stellar UV Irradiation", The Astrophysical Journal Letters, 925 (1): L3, arXiv:2201.02261, Bibcode:2022ApJ...925L...3F, doi:10.3847/2041-8213/ac4968
  11. ↑ Kasper, David; Bean, Jacob L.; Line, Michael R.; Seifahrt, Andreas; Brady, Madison T.; Lothringer, Joshua; Pino, Lorenzo; Fu, Guangwei; Pelletier, Stefan; Stürmer, Julian; Benneke, Björn; Brogi, Matteo; Désert, Jean-Michel (2023), "Unifying High- and Low-resolution Observations to Constrain the Dayside Atmosphere of KELT-20b/MASCARA-2b", The Astronomical Journal, 165 (1): 7, arXiv:2208.04759, Bibcode:2023AJ....165....7K, doi:10.3847/1538-3881/ac9f40