TOI-1431b/MASCARA-5b: A Highly Irradiated Ultrahot Jupiter Orbiting One of the Hottest and Brightest Known Exoplanet Host Stars
Latham, David W.; Stassun, Keivan G.; Wittenmyer, Robert A.; Fischer, Debra A.; Horner, Jonathan; Collins, Karen A.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Antoci, Victoria; Buchhave, Lars A.; Santos, N. C.; Crouzet, Nicolas; Günther, Maximilian N.; Shporer, Avi; Ciardi, David R.; Nowak, Grzegorz; Albrecht, Simon; Fukui, Akihiko; Narita, Norio; Palle, Enric; Snellen, Ignas; Johnson, Marshall C.; Eastman, Jason D.; Jensen, Eric L. N.; Kielkopf, John F.; Luque, Rafael; Knudstrup, Emil; Levine, Alan M.; Twicken, Joseph D.; Daylan, Tansu; Wang, Songhu; Bouma, Luke G.; Komacek, Thaddeus D.; Schwarz, Richard P.; Murgas, Felipe; Grundahl, Frank; Fredslund Andersen, Mads; Clark, Jake T.; Wright, Duncan J.; Smith, Jeffrey C.; Bello-Arufe, Aaron; Bonfils, Xavier; Almenara, Jose-Manuel; Hoyer, Sergio; McLean, Brian; Kawauchi, Kiyoe; Demangeon, Olivier D. S.; Srdoc, Gregor; Dorval, Patrick; Hébrard, Guillaume; Harbeck, Daniel; Cabot, Samuel H. C.; Parviainen, Hannu; Esparza-Borges, Emma; Addison, Brett C.; Jessen-Hansen, Jens; Rabus, Markus; Wong, Ian; Tronsgaard, René; Watanabe, Noriharu; Kiefer, Flavien; Boisse, Isabelle; Louie, Dana R.; Dalal, Shweta; Stangret, Monika; Otten, Gilles P. P. L.; Jan Talens, Geert; Pallé, Pere; Yilmaz, Mesut; Senavci, Hakan Volkan; Diamond, Brendan
Australia, Denmark, United States, France, Netherlands, Portugal, Spain, Japan, Chile, Taiwan, Canada, Croatia, Turkey
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 ${T}_{\mathrm{eff}}={7690}_{-250}^{+400}$ K, resulting in a highly irradiated planet with an incident flux of $\langle F\rangle ={7.24}_{-0.64}^{+0.68}\times $ 109 erg s-1 cm-2 ( ${5300}_{-470}^{+500}\,{S}_{\oplus }$ ) 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.