ExoGemS High-Resolution Transmission Spectroscopy of WASP-76b with GRACES

TL;DR

This study uses high-resolution transmission spectroscopy with GRACES to detect and analyze atomic and molecular species in the atmosphere of exoplanet WASP-76b, revealing new detections and non-detections that inform atmospheric composition and dynamics.

Contribution

First high-resolution optical transmission spectroscopy of WASP-76b with GRACES, detecting multiple atmospheric species and assessing detection limits compared to other instruments.

Findings

Detected Fe I, Na I, and Ca II at >5σ significance.

Tentative detections of Li I, K I, Cr I, and V I.

Non-detections of several species previously observed with other instruments.

Abstract

We present high-resolution transmission spectroscopy of WASP-76b with GRACES/Gemini North obtained as part of the ExoGemS survey. With a broad spectral range of 400-1050 nm and a relatively high resolution of ~66,000, these observations are particularly well-suited to searching for atomic and molecular atmospheric species via the Doppler cross-correlation technique. We recover absorption features due to neutral iron (Fe I), sodium (Na I), and ionized calcium (Ca II) at high significance (>5$\sigma$), and investigate possible atmospheric temperatures and wind speeds. We also report tentative (>3$\sigma$) detections of Li I, K I, Cr I, and V I in the atmosphere of WASP-76b. Finally, we report non-detections of a number of other species, some of which have previously been detected with other instruments. Through model injection/recovery tests, we demonstrate that many of these species are not expected to be detected in our observations. These results allow us to place GRACES and the ExoGemS survey in context with other high-resolution optical spectrographs.