Stingray: Next-Generation Spectral Timing Software

Stingray is a new community-developed spectral-timing software package in Python for astrophysical data.

Stingray logo, outline of a stingray on top of a graph of the power spectrum of an X-ray binary

The Vision

There are a number of official software packages for X-ray spectral fitting (XSPEC, ISIS, Sherpa, …). Such a widely used and standard software package does not exist for X-ray timing, so for now it remains mostly done with custom, proprietary software. During the 2016 workshop The X-ray Spectral-Timing Revolution, a group of X-ray astronomers and developers decided to agree on a common platform to develop a new software package. This software package will merge existing efforts for a timing package in Python and provide the basis for developing spectral-timing analysis tools, and be structured with the best guidelines for modern open-source programming, following the example of Astropy. This software will have an easily accessible scripting interface (possibly a GUI) and a public API for power users. The ultimate goal is to provide the community with a package that eases the learning curve for advanced spectral-timing techniques, with a correct statistical framework.

Overview of Currently Implemented Methods

Currently implemented functionality in this library comprises:

  • loading event lists from fits files of a few missions (RXTE/PCA, NuSTAR/FPM, XMM-Newton/EPIC)
  • constructing light curves from event data, various operations on light curves (e.g. add, subtract, join, truncate)
  • Good Time Interval operations
  • power spectra in Leahy, rms normalization, absolute rms and no normalization
  • averaged power spectra
  • dynamical power spectra
  • maximum likelihood fitting of periodograms/parametric models
  • (averaged) cross spectra
  • coherence, time lags
  • cross correlation functions
  • r.m.s. spectra and lags (time vs energy, time vs frequency); UNDER DEVELOPMENT
  • covariance spectra; UNDER DEVELOPMENT
  • bispectra; UNDER DEVELOPMENT
  • (Bayesian) quasi-periodic oscillation searches
  • simulating a light curve with a given power spectrum
  • simulating a light curve from another light curve and a 1-d (time) or 2-d (time-energy) impulse response
  • simulating an event list from a given light curve _and_ with a given energy spectrum
  • pulsar searches with Epoch Folding, \(Z^2_n\) test

Future Additions

We welcome feature requests! If you need a particular tool that’s currently not implemented or have a new method you think might be usefully implemented in Stingray, please get in touch!

Other future additions we are currently implementing are:

  • bicoherence
  • phase-resolved spectroscopy of quasi-periodic oscillations
  • Fourier-frequency-resolved spectroscopy
  • power colours
  • full HEASARC-compatible mission support
  • pulsar searches with $H$-test
  • binary pulsar searches

This Documentation and Additional Resources

These pages lay out the documentation for the Stingray source library.

Aside from the Stingray API reference, there are a number of tutorial-style documents covering the core library as well as a number of sub-modules. These tutorials are built from executable Jupuyter notebooks available for cloning in a separate notebooks repository.

Further spectral-timing functionality, in particularly command line scripts based on the API defined within Stingray, is available in the package HENDRICS. A Graphical User Interface is under development as part of the project DAVE.

Citing Stingray

If you use Stingray in your data analysis, please cite us! Citations are still the main currency of the academic world, and pointing to citations is the best way to help us ensure that Stingray continues to be supported and we can continue working on it!

Currently, the best way to cite Stingray in papers and other projects is with our Astrophysics Source Code Library entry. Stay tuned for the first version release later in 2018.

Reporting Bugs and Issues, Getting Help, Providing Feedback

We would love to hear from you! We are writing Stingray to be useful to you, so if you encounter problems, have questions, would like to request features or just want to chat with us, please don’t hesitate to get in touch!

The best and easiest way to get in touch with us regarding bugs and issues is the GitHub Issues page. If you’re not sure whether what you’ve encountered is a bug, if you have any questions or need advice getting some of the code to run, or would like to request a feature or suggest additions/changes, you can also contact us via the Slack group or our mailing list.

Please use this link to join Slack or send one of us an email to join the mailing list.

How to get involved

We encourage you to get involved with Stingray in any way you can! First, read through the README. Then, fork the stingray and notebooks repositories (if you need a primer on GitHub and git version control, look here) and work your way through the Jupyter notebook tutorials for the main modules. Once you’ve familiarized yourself with the basics of Stingray, go to the Stingray issues page and try to tackle one! Other ways to get involved are outlined on the project ideas page, along with some astrophysical background/motivation. Finally, you can read these slides from an early talk on Stingray at the Python in Astronomy 2016 conference.

For organizing and coordinating the software development, we have a Slack group and a mailing list – please use this link for Slack or send one of us an email to join.

Previous projects being merged in Stingray

  • Daniela Huppenkothen’s original Stingray
  • Matteo Bachetti’s MaLTPyNT
  • Abigail Stevens’ RXTE power spectra code and phase-resolved spectroscopy code
  • Simone Migliari’s and Paul Balm’s X-ray data exploration GUI commissioned by ESA

Acknowledgments

Thank you to JetBrains for the free use of PyCharm.

Stingray is participating in the Google Summer of Code in 2018 under Open Astronomy and has previously participated in 2017 under the Python Software Foundation, and in 2016 under Timelab.

Table of Contents

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