.. _readme:

X-PSI

An open-source package for neutron star \ X-ray Pulse Simulation and Inference.

|Build Status Main| |Docs| |GitHub Release|

X-PSI is designed to simulate rotationally-modified (pulsed) surface X-ray emission from neutron stars, taking into account relativistic effects on the emitted radiation. This can then be used to perform Bayesian statistical inference on real or simulated astronomical data sets. Model parameters of interest may include neutron star mass and radius (useful to constrain the properties of ultradense nuclear matter) or the system geometry and properties of the hot emitting surface-regions. To achieve this, X-PSI couples code for likelihood functionality (simulation) with existing open-source software for posterior sampling (inference).

It provides the following functionality:

• Simulation of time- and energy resolved X-ray emission (pulse profiles) from the surfaces of neutron stars.
• The facility to implement multiple models for surface patterns, atmospheres, and different instruments.
• Coupling of pulse simulation functionality to statistical sampling software to infer spacetime and geometric parameters from pulse profile data.
• An extensive suite of post-processing software to visualize posteriors and measures of model quality.

For more details on current and planned capabilities, check out the X-PSI documentation <https://xpsi-group.github.io/xpsi/index.html>_.

Installation and Testing

X-PSI has a complex set of dependencies, and is therefore currently best installed from source. The documentation provides step-by-step installation instructions <https://xpsi-group.github.io/xpsi/install.html>_ for Linux and for limited MacOS systems.

Documentation

The documentation for XPSI, including a wide range of tutorials and scripts for running XPSI on HPC systems, can be found at https://xpsi-group.github.io/xpsi/ <https://xpsi-group.github.io/xpsi/>_.

How to get in touch or get involved

We always welcome contributions and feedback! We are especially interested in hearing from you if

• something breaks,
• you spot bugs,
• if there is missing functionality, or you have suggestions for future development,

To get in touch, please open an issue <https://github.com/xpsi-group/xpsi/issues>. Even better, if you have code you'd be interested in contributing, please send a pull request <https://github.com/xpsi-group/xpsi/pulls> (or get in touch and we'll help guide you through the process!).

For more information, you can take a look at the documentation's Contributing page <https://xpsi-group.github.io/xpsi/contributing.html>_. Please also make sure you take a look at the Code of Conduct <https://xpsi-group.github.io/xpsi/code_of_conduct.html>_.

Citing XPSI

If you find this package useful in your research, please provide the appropriate acknowledgment and citation. Our documentation <https://xpsi-group.github.io/xpsi/citation.html>_ provides more detail, including links to appropriate papers and BibTeX entries.

Copyright and Licensing

All content © 2016-2023 the authors. The code is distributed under the GNU General Public License v3.0; see LICENSE <LICENSE>_ for details.

Legacy

An earlier version (pre-v0.5) of this project was named: A prototype open-source package for neutron star X-ray Pulsation Simulation and Inference.

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