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 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.
- Publication:
-
The Astronomical Journal
- Pub Date:
- November 2021
- DOI:
- arXiv:
- arXiv:2108.11403
- Bibcode:
- 2021AJ....162..218C
- Keywords:
-
- Exoplanet atmospheres;
- Transit photometry;
- High resolution spectroscopy;
- 487;
- 1709;
- 2096;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 25 pages, 11 figures, accepted to AJ