A.C.I.D v2 (Accurate Continuum fItting and Deconvolution)

GitHub link: https://github.com/Benjamin-Cadell/ACID_v2

ACID_v2 is a fork of ACID (https://github.com/ldolan05/ACID) from the work of Lucy Dolan for her PhD. ACID_v2 improves on ACID by:

• Updating packages and code to work with newer and stable versions of python.

• Improving memory management so that ACID can be run on MacOS without crashes (ie extending compatibility to all POSIX systems)

• Adding additional kwargs to ACID to tailor output, including verbosity settings, MCMC number of steps, multiprocessing switch, and more.

• Utilising classes for both ACID and the result of ACID, allowing for analysis methods that can be found in the documentation.

• Methods to extract fits formats for common instruments (e.g. ESPRESSO, HARPS, UVES) and to load them directly into ACID.

• Updated documentation and examples

The mathematical functions and method remain the same as ACID and are outlined in Dolan et al. 2024 (https://academic.oup.com/mnras/article/529/3/2071/7624678).

The documentation will be kept up to date with the latest function descriptions until at least 2029.

ACID is a technique that builds on traditional Least-Squares Deconvolution (LSD) by simultaneously fitting the stellar continuum and stellar line profile and performing LSD in effective optical depth.

In a basic sense, ACID simulatenously fits the stellar continuum and profile using a combination of LSD and MCMC techniques (MCMC implementation through emcee). The spectra are then continuum corrected using this continuum fit. LSD is then run on the continuum corrected spectra to return high-resolution line profiles for each spectrum.

For a full outline of ACID’s algorithm and implementation, see the paper or view the package on GitHub.

Please note that ACID v2 now functions as a class, and so the usage is slightly different to ACID v1. Please see the User Guide and the Using ACID page for more information.

User Guide

• Installation and Setup
  • Installing the package
  • Cloning the repository
  • Testing the installation
• Tutorial - Using ACID
  • Quickstart
  • Multiple frames
  • Multiple Orders
  • Using Deterministic profile in MCMC fitting
  • Running ACID Until Convergence
• Results and Plotting
  • Using the Results Class
  • Saving the Result
  • Plotting
• Multiprocessing
  • Best Practices
  • Windows Support
• Using the Data class
• The DataList and loading FITS files
• Analysing the Final Profiles
• Other ACID Functions
  • Continuing sampling
  • Performing LSD
• ACID API
  • Core Classes
  • Utility Functions
  • Legacy ACID Functions

License and Attribution

Copyright 2025, Benjamin Cadell.

ACID is free software made available under the MIT License.

If you make use of ACID or ACID_v2 in your work please cite the original work by L.Dolan (L.Dolan et al, 2024): https://academic.oup.com/mnras/article/529/3/2071/7624678.