TOI-1431b/MASCARA-5b: A Highly Irradiated Ultrahot Jupiter Orbiting One of the Hottest and Brightest Known Exoplanet Host Stars

Brett C. Addison, Emil Knudstrup, Ian Wong, Guillaume Hébrard, Patrick Dorval, Ignas Snellen, Simon Albrecht, Aaron Bello-Arufe, Jose Manuel Almenara, Isabelle Boisse, Xavier Bonfils, Shweta Dalal, Olivier D.S. Demangeon, Sergio Hoyer, Flavien Kiefer, N. C. Santos, Grzegorz Nowak, Rafael Luque, Monika Stangret, Enric PalleRené Tronsgaard, Victoria Antoci, Lars A. Buchhave, Maximilian N. Günther, Tansu Daylan, Felipe Murgas, Hannu Parviainen, Emma Esparza-Borges, Nicolas Crouzet, Norio Narita, Akihiko Fukui, Kiyoe Kawauchi, Noriharu Watanabe, Markus Rabus, Marshall C. Johnson, Gilles P.P.L. Otten, Geert Jan Talens, Samuel H.C. Cabot, Debra A. Fischer, Frank Grundahl, Mads Fredslund Andersen, Jens Jessen-Hansen, Pere Pallé, Avi Shporer, David R. Ciardi, Jake T. Clark, Robert A. Wittenmyer, Duncan J. Wright, Jonathan Horner, Karen A. Collins, Eric L.N. Jensen, John F. Kielkopf, Richard P. Schwarz, Gregor Srdoc, Mesut Yilmaz, Hakan Volkan Senavci, Brendan Diamond, Daniel Harbeck, Thaddeus D. Komacek, Jeffrey C. Smith, Songhu Wang, Jason D. Eastman, Keivan G. Stassun, David W. Latham, Roland Vanderspek, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Dana R. Louie, Luke G. Bouma, Joseph D. Twicken, Alan M. Levine, Brian McLean

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


We present the discovery of a highly irradiated and moderately inflated ultrahot Jupiter, TOI-1431b/MASCARA-5 b (HD 201033b), first detected by NASA's Transiting Exoplanet Survey Satellite mission (TESS) and the Multi-site All-Sky Camera (MASCARA). The signal was established to be of planetary origin through radial velocity measurements obtained using SONG, SOPHIE, FIES, NRES, and EXPRES, which show a reflex motion of K = 294.1 1.1 m s-1. A joint analysis of the TESS and ground-based photometry and radial velocity measurements reveals that TOI-1431b has a mass of M p = 3.12 0.18 M J (990 60 M ⊕), an inflated radius of R p = 1.49 0.05 R J (16.7 0.6 R ⊕), and an orbital period of P = 2.650237 0.000003 days. Analysis of the spectral energy distribution of the host star reveals that the planet orbits a bright (V = 8.049 mag) and young ({0.29-0.19+0.32 Gyr) Am type star with R eff=7690-250+400 K, resulting in a highly irradiated planet with an incident flux of F =7.24-0.64+0.68 × 109 erg s-1 cm-2 (5300-470+500 S) and an equilibrium temperature of T eq = 2370 70 K. TESS photometry also reveals a secondary eclipse with a depth of 127-5+4 ppm as well as the full phase curve of the planet's thermal emission in the red-optical. This has allowed us to measure the dayside and nightside temperature of its atmosphere as T day = 3004 64 K and T night = 2583 63 K, the second hottest measured nightside temperature. The planet's low day/night temperature contrast (∼420 K) suggests very efficient heat transport between the dayside and nightside hemispheres. Given the host star brightness and estimated secondary eclipse depth of ∼1000 ppm in the K band, the secondary eclipse is potentially detectable at near-IR wavelengths with ground-based facilities, and the planet is ideal for intensive atmospheric characterization through transmission and emission spectroscopy from space missions such as the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.

Original languageEnglish (US)
Article number292
JournalAstronomical Journal
Issue number6
StatePublished - Dec 1 2021

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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