TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in Its Atmosphere

November 2021 • 2021AJ....162..218C

Authors • Cabot, Samuel H. C. • Bello-Arufe, Aaron • Mendonça, João M. • Tronsgaard, René • Wong, Ian • Zhou, George • Buchhave, Lars A. • Fischer, Debra A. • Stassun, Keivan G. • Antoci, Victoria • Baker, David • Belinski, Alexander A. • Benneke, Björn • Bouma, Luke G. • Christiansen, Jessie L. • Collins, Karen A. • Goliguzova, Maria V. • Hagey, Simone • Jenkins, Jon M. • Jensen, Eric L. N. • Kidwell, Richard C., Jr. • Laloum, Didier • Massey, Bob • McLeod, Kim K. • Latham, David W. • Morgan, Edward H. • Ricker, George • Safonov, Boris S. • Schlieder, Joshua E. • Seager, Sara • Shporer, Avi • Smith, Jeffrey C. • Srdoc, Gregor • Strakhov, Ivan A. • Torres, Guillermo • Twicken, Joseph D. • Vanderspek, Roland • Vezie, Michael • Winn, Joshua N.

Abstract • We present the discovery of TOI-1518b-an ultra-hot Jupiter orbiting a bright star (V = 8.95). The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with Rp = 1.875 ± 0.053 RJ, and exhibits several interesting properties, including a misaligned orbit ( ${240.34}_{-0.98}^{+0.93}$ degrees) and nearly grazing transit ( $b={0.9036}_{-0.0053}^{+0.0061}$ ). The planet orbits a fast-rotating F0 host star (Teff ≃ 7300 K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of 364 ± 28 ppm and a significant phase-curve signal, from which we obtain a relative day-night planetary flux difference of roughly 320 ppm and a 5.2σ detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultra-hot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (5.2σ), at ${K}_{p}={157}_{-44}^{+68}$ km s-1 and ${V}_{\mathrm{sys}}=-{16}_{-4}^{+2}$ , adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii ≳1.78 RJ, which may be due to observational bias. With an equilibrium temperature of Teq = 2492 ± 38 K and a measured dayside brightness temperature of 3237 ± 59 K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion.


IPAC Authors


Jessie Christiansen

Associate Scientist