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

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 R p = 1.875 ± 0.053 R J , and exhibits several interesting properties, including a misaligned orbit (240.34 +0.93 −0.98 degrees) and nearly grazing transit (b = 0.9036 +0.0061 −0.0053 ). The planet orbits a fastrotating F0 host star (T eff 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.

Mining the Ultra-Hot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species

“…Per contra, the Fe I and Fe II detections in KELT-9 b show no significant Doppler-shift with respect to the rest frame of the planet (Hoeijmakers et al 2019). Cabot et al (2021) recently reported a detection of Fe I in the atmosphere of the ultra-hot Jupiter TOI-1518 b, blue-shifted by ∼ 2 km s −1 , and a tentative detection of Fe II, with a blue-shift of ∼ 4 km s −1 .…”

TESS Giants Transiting Giants II: The hottest Jupiters orbiting evolved stars

“…Given that the systems studied here have evolved from hot stars with thin convective envelopes on the main sequence to giants with thick convective envelopes, measuring the obliquity of these newly confirmed planets can distinguish between these theorized mechanisms for spin-orbit alignment in hot Jupiter systems. Measuring the Rossiter-McLaughlin (RM) effect (McLaughlin 1924;Rossiter 1924) for these systems with extreme precision radial velocity instruments could reveal trends of planetary system obliquities with respect to stellar mass (Rubenzahl et al 2021;Cabot et al 2021), and constrain models of hot Jupiter formation (e.g., Dawson & Johnson 2018;Albrecht et al 2021). Stellar obliquity can also be constrained via asteroseismology (Huber et al 2013) and thus future asteroseismic detections for these systems, in combination with future RM measurements, could reveal true system obliquities.…”

A survey of sodium absorption in ten giant exoplanets with high-resolution transmission spectroscopy

“…This is small in comparison to the systemic velocity and planetary radial velocity, and should not significantly impact our results. For fast rotating stars with broadened stellar lines, the radial velocity shift does not have a significant effect on the planetary transmission spectrum and can be ignored (Casasayas-Barris et al 2018Cabot et al 2021). However, since we are conducting a homogeneous survey using a variety of data, we opt to correct for the stellar radial velocity to keep the method consistent for all targets.…”

“…First, spectra acquired with ground-based instruments are contaminated by absorption from Earth's atmosphere -in the optical domain, telluric water and oxygen are the dominant sources of contamination (Smette et al 2015;Kausch et al 2015;Wyttenbach et al 2015;Allart et al 2017;Langeveld et al 2021). Additionally, sodium absorption from interstellar sources (Casasayas-Barris et al 2018;Chen et al 2020b;Cabot et al 2021) or sodium emission from the sky (Casasayas- Barris et al 2017) can be detrimental when analysing sodium in exoplanet atmospheres. Next, the spectra must be Doppler shifted to account for stellar, systemic, and planetary radial velocities to make sure that atmospheric features are recovered in the planetary rest frame.…”