PolPy

polpy is a universal plugin for 3ML developed to analyse polarization data from X-ray/gamma-ray scattering polarimeters. In particular, it is developed to perform polarimetry of high-energy transients, such as gamma-ray bursts (GRBs). It is based polarpy (Burgess, Kole et al. 2019, A&A) tool that was developed for POLAR analysis. It can be used for current and future scattering polarimeters, provided standardized data and response format (docs/Data_and_Response_Format_For_PolPy.pdf) and a defined coordinate convention are followed (docs/Coordinate_Defintions_and_Transforms_For_PolPy.pdf).

Contents

• Installation
• Package layout
• Quick start
• Data and response file formats
• License
• Authors

Installation

polpy is available on PyPI and uses modern Python packaging via pyproject.toml. We recommend installing it inside a virtual environment (using conda, venv, or your preferred environment manager) to prevent dependency conflicts.

Standard Installation

To install the latest stable version directly from PyPI, run:

pip install polpy

Package layout

polpy/
├── polpy/
│   ├── poldata.py            # PolData: read raw polarization event files, compute PA offset
│   ├── polresponse.py        # PolResponse: read + interpolate the polarization response
│   └── polarizationlike.py   # PolarizationLike: the 3ML plugin (likelihood, fitting, display)
├── docs/
│   ├── Data_and_Response_Format_For_PolPy.pdf
│   └── Coordinate_Defintions_and_Transforms_For_PolPy.pdf
└── tests/                    # pytest unit tests

Data and response file formats

Two reference documents ship with the repo:

• docs/Data_and_Response_Format_For_PolPy.pdf — layout of the POLEVENTS event FITS extension and the .prsp response FITS extensions (INEBOUNDS, SABOUNDS, INPAVALS, SPECRESP POLMATRIX, SPECRESP UNPOLMATRIX)
• docs/Coordinate_Defintions_and_Transforms_For_PolPy.pdf — instrument reference frame, local-tangent-plane frame, and the IAU polarization-angle offset convention used by PolData.get_pa_offset()

License

GPL-3.0.

Authors

Sujay Mate, Hancheng Li, Utkarsh Pathak, Yashowardhan Rai, Nicholas De Angelis, Varun Bhalerao, Merlin Kole.