Tutorial: End-to-End Atmospheric Characterization of WASP-77Ab

Francesco Amadori and Paolo Giacobbe

This tutorial provides a step-by-step guide to performing a complete atmospheric characterization of the hot Jupiter WASP-77Ab using GUIBRUSHR. The workflow covers the full analysis chain, from the processing of high-resolution (HR) ground-based spectra to the retrieval of atmospheric properties at low resolution (LR) from space-based data, and their combination into a joint multi-resolution retrieval. By following this tutorial, users will become familiar with every major module of the software.

The analysis presented here is based on the datasets originally published in the literature and used to validate GUIBRUSHR. On the HR side, we use dayside emission observations of WASP-77Ab acquired with the Immersion GRating INfrared Spectrometer (IGRINS; Park et al. 2014, Mace et al. 2016) at the Gemini South Observatory, as described in Line et al. (2021). On the LR side, we use the secondary-eclipse emission spectrum obtained with the Near-Infrared Spectrograph (NIRSpec; Jakobsen et al. 2022, Birkmann et al. 2022) on board the James Webb Space Telescope (JWST), as published by August et al. (2023). The combined multi-resolution analysis follows the approach presented in Smith et al. (2024).

Tutorial Sections

• Target: WASP-77Ab
• Datasets
  • High-Resolution: IGRINS at Gemini South
  • Low-Resolution: JWST/NIRSpec
• Prerequisites
  • Provided opacity line lists
• Telluric Removal
  • Interface Overview
  • General Settings (First Row)
  • Telluric Method and Order Selection (Second Row)
  • Masking Parameters (Third Row)
  • PCA Configuration (Fourth Row)
  • Running the Telluric Removal
• Forward Modeling
  • Main Configuration Panel
  • Parameters
  • Planet + Data
  • Clouds/Haze
  • Temperatures
  • Temperatures2 (Bezier Nodes)
  • VMR
  • Equilibrium
  • Molecules
  • Condensed Elements
  • Generating the Model
• Cross-Correlation
  • General Configuration
  • Cross-Correlation – Planetary Trail
  • Cross-Correlation – \(K_p\)–\(V_{\mathrm{sys}}\) Map
• HR Retrieval
• LR Retrieval
• Combined Retrieval
• Retrieval Analysis
• Synthetic Generator
• Database and Folders Interactions

Overview of the Tutorial Workflow

This tutorial is organized into the following sections, each corresponding to a dedicated page in the documentation. Together, they walk the user through the full GUIBRUSHR analysis chain:

1. Telluric Removal (Telluric Removal): Removal of Earth’s atmospheric contamination from the HR dataset using masking procedures and Principal Component Analysis (PCA).

2. Forward Modeling (Forward Modeling): Generation of synthetic atmospheric spectra by configuring planetary parameters, chemical composition, and temperature–pressure profiles.

3. Cross-Correlation (Cross-Correlation): Detection of molecular species in the HR spectra via the cross-correlation function (CCF) technique applied to forward models.

4. HR Retrieval (HR Retrieval): Bayesian atmospheric retrieval using only the IGRINS high-resolution dataset.

5. LR Retrieval (LR Retrieval): Bayesian atmospheric retrieval using only the JWST/NIRSpec low-resolution dataset.

6. Combined Retrieval (Combined Retrieval): Joint multi-resolution retrieval combining the HR and LR datasets simultaneously.

7. Retrieval Analysis (Retrieval Analysis): Inspection and visualization of retrieval results, including posterior distributions, best-fit models, and cross-correlation diagnostics.

8. Synthetic Generator (Synthetic Generator): Generation of synthetic HR observations for testing and planning purposes.

9. Database and Folders Interactions (Database and Folders Interactions): Management of the internal SQLite3 database, instrument configurations, target properties, and folder structures.

Users who wish to follow the tutorial from start to finish should proceed in the order listed above. However, each section is designed to be self-contained, so experienced users may jump directly to the module of interest.