2023 Sagan Summer Workshop

Characterizing Exoplanet Atmospheres: The Next Twenty Years

Hands-On Sessions

The topics for the 2023 Sagan Workshop hands-on sessions are listed below. Check back for more details as we develop them further!

Comparison of JWST Data with High-resolution Data from Ground-based Telescopes

Hands-on Session I: Reducing JWST Data: from raw data to light curves

JWST observations offer the potential for amazing advancements in the field of exoplanet atmospheric characterization. However, the raw data produced by JWST first needs careful processing to be able to perform such measurements. The goal of this first hands-on session is to teach you how to go from raw JWST data to spectroscopic light curves for a transiting planet; a process called “data reduction”. During the session, you will reduce real observations from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program with your choice of working on NIRSpec/G395H transit observations of WASP-39b or MIRI/LRS eclipse observations of WASP-43b.

Topics covered in the session will include:

  • Downloading JWST data (via a browser or an API)
  • An overview of the open-source Eureka! data analysis pipeline for time-series observations
  • The general steps required to reduce JWST data, including calibration steps, background subtraction, and optimal extraction
  • How to set the “Eureka! Control Files” (ECFs) for Stages 1-4
  • How to tweak ECF settings to see how each one impacts the final quality of the data and get the best reduction you can

Hands-on Session II: Fitting JWST Data: from light curves to planet spectra

In this hands-on session, you will learn how to fit light curves to measure the transmission (or emission) spectra of transiting exoplanets. In particular, you will learn how to fit real spectroscopic lightcurves from JWST using the open-source Eureka! package. This session will build on the spectroscopic light curves produced during Session I, but all of the data files required for this session will be available for those who do not attend Session I or struggle to get a good reduction themselves.

Topics covered in the session will include:

  • Transmission spectroscopy and emission spectroscopy
  • Bayesian inference, optimization algorithms, and sampling algorithms
  • Python packages for modelling exoplanet signals
  • Methods for removing systematic noise
  • How to fit JWST observations with Eureka!'s Stage 5
  • How to tweak Eureka!'s Stage 5 “Eureka! Control File” and “Eureka! Parameter File” to best fit your data

Atmospheric Modeling

Hands-on Session III: Forward Modeling with PICASO

In this hands on session you will learn how to conduct the steps taken to create a small grid of atmospheric models, similar to those used in the analysis of the JWST Transiting Exoplanet Early Release Science Team's WASP-39b observation (see Ahrer et al., Rustamkulov et al., Alderson et al., and Feistein et al., 2003). Then, you will learn how to use grid models to conduct basic fits to data in order to make physical inferences of a planet's atmosphere. In all the process will be composed of:

  • Understand how to use PICASO to create the transmission spectrum of an exoplanet
  • Understand how to use PICASO to create a 1D radiative convective climate model
  • Analyze the result of a radiative convective model and understand the model outputs
  • Create a small grid of models over a range of metallicities and carbon to oxygen ratios
  • Leverage the JWST Transiting Exoplanet Early Release Science Team's Prism data (Rustamkulov et al. 2023) to fit models to data and make physical inferences about the planet's metal enrichment and carbon to oxygen ratio

Hands-on Session IV: Retrievals using petitRADTRANS

In this session you will learn how to use petitRADTRANS (pRT) to calculate atmospheric spectra for JWST retrievals. We will make use of the transmission spectra derived for WASP-39b in the first hands-on sessions. An input spectrum will also be provided.

The following points will be covered:

  • Calculation of transmission and emission spectra with pRT and the effect of clouds.
  • Walkthrough pRT's analysis tools: contribution functions, opacity plots and chemical equilibrium abundances
  • Running a small retrieval on JWST data with pRT's retrieval package and PyMultiNest.

More specifically this will include the following steps:

  • Forward model construction (efficiency and level of complexity)
  • Prior setup (cube transformation, prior range and shape)
  • PyMultiNest setup (number of live points, sampling efficiency)
  • Analysis of retrieval results (posterior plots, Bayes factor analysis, etc.)


Workshop Code of Conduct.

2023 Workshop home page

(last updated February 13th, 2023 10:02:41)