Researchers Discover An Ultra-Hot Jupiter, TOI-1431b, Where Temperatures Reach 2900 K (Planetary Science)

Key points:

  • Researchers, with the help of NASA, have discovered a new planet
  • Called TOI-1431b or MASCARA-5b, it is about 490 light years away from Earth and too hot to support life
  • The planet has the second hottest nightside temperature ever measured and its daytime temperatures can reach 2,700C.

Astrophysicist Dr Brett Addison and colleagues have presented the discovery of the transiting ultra-hot Jupiter, TOI-1431 b also called MASCARA-5b (HD 201033 b). This planet orbits one of the hottest (Teff = 7690 K) and brightest (VT ∼ 8.0) of the known host stars with a period of just Pp = 2.65022 d, resulting in it receiving a high amount of insolation flux and being moderately inflated. Their study recently appeared on Journal Arxiv.

TOI-1431/MASCARA-5 (HD 201033) was observed with space-based photometry by TESS and ground-based photometry from several facilities. TOI 1431 b/MASCARA-5 b (HD 201033 b), 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 m s¯1.

In the present study, Addison and colleagues obtained follow-up spectroscopic observations from several ground-based facilities as well as high-contrast imaging on the Keck II telescope to establish the planetary nature of the transit signals detected by TESS and the Multi-site All-Sky CAmeRA.

A joint analysis of the TESS light curve, groundbased light curves from MuSCAT2 and LCOGT, and radial velocities from SONG, SOPHIE, FIES, NRES, and EXPRES instruments results in a planet radius of Rp = 1.51 RJ (16.9 R) (1.51 times that of the radius of jupiter) and a planet mass of 3.14 MJ, corresponding to a bulk density of 1.18 g cm¯3 .

The planet orbits a bright (V = 8.049 mag) and young (0.29 Gyr) Am type star with Teff = 7690 K, resulting in a highly irradiated planet with an incident flux of hFi = 7.24 × 109 erg s¯1 cm¯2 (5300 S) and an equilibrium temperature of Teq = 2370 K.

The spectroscopic stellar line profile map of TOI-1431 taken with FIES during and after the transit of TOI-1431 b in an attempt to observe the Doppler shadow cast by the planet. The dashed line indicates the end of the transit. There is a gap in the data around the middle of the transit (in the diagram, this region takes the values from the last CCF before the data gap). If the planet signal was strong enough to be detected, it would appear as a dark blue trail in the line profile residuals between ingress and egress. No clear signal is present in the data indicating that they are not able to detect the Doppler shadow of the planet and measure its spin-orbit alignment. © Addison et al.

They also detected planet’s phase curve and secondary eclipse from the TESS photometry, which provided them exciting opportunity to measure the planet’s dayside and nightside temperatures as Tday = 2983 K and Tnight = 2556 K, respectively, when assuming zero dayside geometric albedo. Among the population of hot/ultra-hot Jupiters, TOI-1431 b has the second highest measured nightside temperature and day-night heat recirculation efficiency.

“The planet’s low day/night temperature contrast (∼400 K) suggests very efficient heat transport between the dayside and nightside hemispheres.”

Finally, they concluded that 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 with the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey.

“The discovery and characterization of planets orbiting Am stars, for which few planets have been found, provides good opportunities to probe the tidal interactions between Jovian planets and hot host stars and the potential mechanisms responsible for the creation and evolution of Am stars.”

Featured image: Artist impression of TOI-1431b in orbit.(Supplied: University of Southern Queensland)

Reference: Brett Christopher Addison, Emil Knudstrup, Ian Wong, Guillaume Hebrard, Patrick Dorval, Ignas Snellen, Simon Albrecht, Aaron Bello-Arufe, Jose-Manuel Almenara, Isabelle Boisse, Xavier Bonfils, Shweta Dalal, Olivier Demangeon, Sergio Hoyer, Flavien Kiefer, N. C. Santos, Grzegorz Nowak, Rafael Luque, Monika Stangret, Enric Palle, Rene Tronsgaard, Victoria Antoci, Lars A. Buchhave, Maximilian N. Gunther, 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-Hanse, Pere Palle, 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, “TOI-1431b/MASCARA-5b: A Highly Irradiated Ultra-Hot Jupiter Orbiting One of the Hottest & Brightest Known Exoplanet Host Stars”, ArXiv, pp. 1-38, 2021.

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