# ExoCTK Package Documentation¶

ExoCTK is an open-source, modular data analysis package focused primarily on atmospheric characterization of exoplanets.

The subpackages currently included are:

Contamination and Visibility Calculators Groups and Intrgrations Calculator Transit Light-­Curve Fitting Tools Limb-­Darkening Calculator Phase Constraint Calculator Atmospheric Forward Modeling - Currently only available through the website.

All source code can be found on GitHub.

There is also a website where all current tools are available through interactive applications.

## User Documentation¶

Contamination and Visibility Calculator

The Contamination Overlap tool is made up of two calculators: the visibility calculator, and the contamination calculator. The visibility calculator will determine at what position angles (PAs) your target is visible and when. The output results come in the form of interactive Bokeh plots, but users also have the option of downloading their data in an ascii file format. The contamination calculator will determine the percentage of spectral contamination that lands on your target at every PA. The visibility calculator is currently available for all JWST instruments, and the contamination calculator will be released for NIRISS (Mode: Single Object Slitless Spectroscopy), NIRCam (Mode: Grism Time Series), and MIRI (Mode: Low-Resolution Spectroscopy).

Groups and Integrations Calculator

The groups_integrations tool is a JWST observation planning tool designed with exoplanet observations in mind. Given a potential observation (which requires transit time, and an estimate of model and magnitude for the host star, and specifics of instrument setup) it’s simple to get an optimized groups and integrations plan for the observation. The example notebook also outlines cases for batch demos – testing many transits/sources in a given instrument setup, or figuring out which instrument setup is best for a given transit.

The Groups and Integrations Calculator runs with pre-sampled pandeia data in the background – so it can have the power of those carefully built instrument models, but still run 100 times faster.

Lightcurve Fitting Tool

The light-curve fitting tool fits large numbers of spectroscopic light curves simultaneously while sharing model parameters across wavelengths and visits. It includes multiple uncertainty estimation algorithms and a comprehensive library of physical and systematic model components that are fully customizable.

Limb Darkening Calculator

The limb_darkening tool calculates limb-darkening coefficients for a specified stellar model, plotting results versus µ and wavelength. It uses high spectral resolution stellar atmospheric models, which are a necessity given JWST’s expected precision.

Atmospheric Retrievals

The atmospheric_retrievals subpackage within the exoctk package currently contains a module for performing retrievals via the PLATON package. This Jupyter notebook contains a demo of how to use the platon_wrapper module.

Users who wish to use the atmospheric_retrievals tools may do so by installing the exoctk package. Please see the installation instructions for further details.

Phase Constraint Calculator

The Phase Constraint Calculator provides a simple interface for calculating JWST observation start windows in phase-space for both, transits and eclipse observations. This allows the user to quickly calculate minimum and maximum phase values that serve as inputs for the APT special requirements section when planning your observations.

## Installation Instructions and Notebook Availability¶

To install the ExoCTK package one can follow the instructions listed in our README available here on GitHub.

There are also several Jupyter Notebooks available for users to aid in learning how to use the various tools included in the ExoCTK package which can be found within the ‘Notebooks’ folder following download of the ExoCTK repository or for viewing online here.

1. Send an email from your mailbox to exoctk-news-subscribe-request@maillist.stsci.edu