First Results from WINERED: Detection of Emission Lines from Neutral Iron and a Combined Set of Trace Species on the Dayside of WASP-189 b

TL;DR

This paper reports the first detection of emission lines from the dayside atmosphere of the ultra-hot Jupiter WASP-189 b using the WINERED spectrograph, revealing key atomic and trace species that inform atmospheric structure.

Contribution

It demonstrates the capabilities of WINERED for high-resolution emission spectroscopy of exoplanets and reports the first detection of specific atomic and trace species in an UHJ's atmosphere.

Findings

Detected neutral iron emission lines with S/N=6.3

Tentative detection of neutral magnesium and silicon

Combined detection of trace species mainly from Cr and Al

Abstract

Ground and space-based observations have revealed that Ultra Hot Jupiters (UHJs,~$T_{\rm{eq}} > 2200 \ \rm{K}$) typically have inverted thermal profiles, while cooler hot Jupiters have non-inverted ones. This shift is theorized due to the onset of strong optical absorbers like metal oxides (e.g., TiO, VO), metal hydrides (e.g. FeH), atomic species (e.g., Fe, Ti), and ions (e.g., H$^-$). High-resolution spectroscopy is valuable for characterizing the thermal, chemical, and dynamical atmospheric structures due to its sensitivity to detailed spectral line shapes. The newly commissioned WINERED high-resolution spectrograph ($R\sim68,000$) on the Magellan Clay 6.5 m telescope enhances capabilities with its high throughput in the J-band (1.13-1.35 $\mu$m), capturing strong spectral features from key atmospheric species. In this study, we report detecting the dayside atmosphere of the UHJ WASP-189 b at a $S/N\sim10$, marking the first exoplanet atmosphere detection in emission with WINERED. Individually, we identify strong neutral iron (Fe) emission lines at a $S/N=6.3$, and tentatively detect neutral magnesium (Mg) and silicon (Si) at a $S/N>4$. Although not individually detected, we detect a combined set of trace species at a $S/N=7.2$, which is attributed mostly to neutral chromium (Cr) and aluminum (Al), alongside magnesium and silicon. These results help refine the understanding of key atmospheric species that influence the thermal structure of WASP-189 b and UHJs more broadly.