Unifying High- and Low-resolution Observations to Constrain the Dayside Atmosphere of KELT-20b/MASCARA-2b

Abstract

We present high-resolution dayside thermal emission observations of the exoplanet KELT-20b/MASCARA-2b using the MAROON-X spectrograph. Applying the cross-correlation method with both empirical and theoretical masks and a retrieval analysis, we confirm previous detections of Fe i emission lines and we detect Ni i for the first time in the planet (at 4.7σ confidence). We do not see evidence for additional species in the MAROON-X data, including notably predicted thermal inversion agents TiO and VO, their atomic constituents Ti i and V i, and previously claimed species Fe ii and Cr i. We also perform a joint retrieval with existing Hubble Space Telescope/WFC3 spectroscopy and Spitzer/IRAC photometry. This allows us to place bounded constraints on the abundances of Fe i, H2O, and CO, and to place a stringent upper limit on the TiO abundance. The results are consistent with KELT-20b having a solar to slightly supersolar composition atmosphere in terms of the bulk metal enrichment, and the carbon-to-oxygen and iron-to-oxygen ratios. However, the TiO volume mixing ratio upper limit (10−7.6 at 99% confidence) is inconsistent with this picture, which, along with the nondetection of Ti i, points to sequestration of Ti species, possibly due to nightside condensation. The lack of TiO but the presence of a large H2O emission feature in the WFC3 data is challenging to reconcile within the context of 1D self-consistent, radiative-convective models.

The Roasting Marshmallows Program with IGRINS on Gemini South I: Composition and Climate of the Ultrahot Jupiter WASP-18 b

“…Second, UHJs require a more complex parameterization of the abundance profiles of (at least) H 2 O and OH, and an estimate of the atomic oxygen produced via thermal dissociation (see also Kasper et al 2023). This is to be implemented in future work.…”

“…In order to obtain quantitative constraints on the molecular abundances and temperature profile (and subsequent products like the atmospheric metallicity and C/O ratio) we must perform an atmospheric retrieval. Following Line et al (2021) and Kasper et al (2021Kasper et al ( , 2023, we applied the Brogi & Line (2019) crosscorrelation-to-log-likelihood retrieval framework to derive the molecular volume mixing ratios and the vertical temperature structure. While going through the retrieval process we gleaned critical insights into the performance of two HRCCS retrieval frameworks: "free retrievals" and "1D-RCTE grid retrievals" ("gridtrieval").…”

Retrieval Survey of Metals in Six Ultrahot Jupiters: Trends in Chemistry, Rain-out, Ionization, and Atmospheric Dynamics

“…Our findings are consistent with recent work from low-resolution retrievals, which showed at or near stellar abundances of alkali metals in hot Jupiters (e.g., ). On the other hand, recent high-resolution dayside observations of MAS-CARA-2 b and other ultrahot Jupiters have shown evidence for superstellar abundances (Cont et al 2022;Kasper et al 2023), indicating that there may be some variation in abundances of Fe in UHJs. Neutral Fe remains gaseous down to temperatures of ∼1350 K at 0.1 mbar (see Table 3), does not strongly ionize until high temperatures (see Figure 4), and is the dominant carrier of iron for these UHJs (Visscher et al 2010).…”

“…A wide range of chemical species has been observed in UHJs (e.g., Casasayas-Barris et al 2018;Hoeijmakers et al 2019;Seidel et al 2019;Ben-Yami et al 2020;Cont et al 2021;Merritt et al 2021;Kesseli et al 2022;van Sluijs et al 2023). In particular, gaseous Fe has been shown to be prevalent in a number of UHJs, under both primary and secondary eclipse observations (e.g., Hoeijmakers et al 2018Hoeijmakers et al , 2020aNugroho et al 2020;Pino et al 2020;Yan et al 2020;Casasayas-Barris et al 2022;Kasper et al 2023).…”

CRIRES+ detection of CO emissions lines and temperature inversions on the dayside of WASP-18b and WASP-76b

“…The discovery of temperature inversions is normally achieved by detecting spectral features in emission with either high-or low-resolution spectroscopy. For example, atomic iron (Fe I) emission lines have been detected with high-resolution spectroscopy in KELT-9b (Pino et al 2020;Kasper et al 2021), WASP-189b (Yan et al 2020), WASP-33b (Nugroho et al 2020;Cont et al 2021;Herman et al 2022), and KELT-20b (Yan et al 2022b;Borsa et al 2022;Johnson et al 2023;Kasper et al 2023); carbon monoxide (CO) emission lines have been detected in WASP-189b, WASP-33b, and MASCARA-1b (Yan et al 2022a;van Sluijs et al 2022;Holmberg & Madhusudhan 2022). A list of discovered chemical species with high-resolution emission observations is presented in Table 1.…”