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

Abstract

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 T 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.

Patchy nightside clouds on ultra-hot Jupiters: General Circulation Model simulations with radiatively active cloud tracers

“…The lefthand panel of Figure 1 displays the evolution of the effective temperature of TOI-1431b, showing the impacts of the early evolution of TOI-1431 on the irradiation received by TOI-1431b. Note that we show results from each MESA model to an age of 0.61 Gyr, consistent with the 1σ upper limit on the system age (Addison et al 2021).…”

“…For all cases, we assume that the maximum of heat deposition occurs at the very center of the planet, in line with our motivation described above to set upper limits on the predicted planetary radius for a given heating rate in our model. We assume a planet mass of 3.12 M Jup (Addison et al 2021) for all cases, and we vary the initial planet radius from 2.5 − 4 R Jup given the unknown initial entropy post-formation (Marleau & Cumming 2014, Berardo et al 2017. We find that the assumed initial radius does not affect the present-day properties of TOI-1431b due to its short ( 10 Myr) Kelvin-Helmoltz contraction timescale (Ginzburg & Sari 2015, Mol Lous & Miguel 2020) -as a result, we only display results from the case with an intermediate initial radius of 3 R Jup .…”

“…Recent TESS discoveries and Spitzer characterization have enabled the study of hot and ultra-hot Jupiters as a population (see Figure 17 of Wong et al 2021). These discoveries include TOI-1431b, which is a young (≈ 0.3 Ga) ultra-hot Jupiter with an equilibrium temperature of ≈ 2370 K that was discovered and characterized by Addison et al (2021) and Stangret et al (2021). TOI-1431b lies in the regime just hotter than the transition point from hot to ultra-hot Jupiters, and similar to HAT-P-7b (Bell et al 2021) it has a surprisingly small day-to-night temperature contrast due to an observed high nightside brightness temperature in the TESS bandpass.…”

An Aligned Orbit for the Young Planet V1298 Tau b

“…V1298 Tau b joins a growing number of planets in young stellar associations with measured spin-orbit angles, including DS Tuc Ab (Zhou et al 2020;Montet et al 2020;Benatti et al 2021), AU Mic b (Hirano et al 2020;Martioli et al 2020;Palle et al 2020;Addison et al 2021b) et al 2021a). The aforementioned planets in young associations, TOI-942 b, and KELT-20 b, have all found to have aligned orbits, Kepler-63 b, KELT-9 b, and TOI-1431 b/ MASCARA-5 b are on polar orbits.…”

Nodal Precession and Tidal Evolution of Two Hot Jupiters: WASP-33 b and KELT-9 b

“…If such a discrepancy exists, it would be a telltale sign of migration and allow us to estimate how recently migration must have occurred, with the caveat that winds and other energy transport mechanisms in the planetary atmospheres could dilute such a signal. High nightside temperatures on the order of 2500 to 3000 K have indeed been observed for exoplanets TOI-1431 b/MASCARA-5 b (Addison et al 2021) and KELT-9 b (Wong et al 2020), though in both cases current models explain these temperatures with atmospheric energy transport.…”