BXA

Spec sheet

Purpose

BXA connects Xspec and Sherpa X-ray spectral analysis environments to UltraNest for Bayesian parameter estimation and model comparison.Read 5 Oct 2026 · johannesbuchner.github.io

Support

The project directs users to file bug reports and feedback as GitHub issues and asks bug reports to include operating system, Sherpa or Xspec version, setup details, and reproduction steps.Read 5 Oct 2026 · johannesbuchner.github.io

Automated fitting

The fitting algorithm explores parameter spaces without requiring good starting points and runs until convergence.Read 5 Oct 2026 · johannesbuchner.github.io

Installation

BXA can be installed with pip or conda and requires either Sherpa or Xspec to be installed and configured.Read 5 Oct 2026 · johannesbuchner.github.io

Intended use

The documentation highlights systematic analysis of large datasets, comparing multiple models, and analyzing low-count datasets with realistic models.Read 5 Oct 2026 · johannesbuchner.github.io

Model comparison

It computes model evidence for Bayes factors and supports comparing models that are not nested.Read 5 Oct 2026 · johannesbuchner.github.io

Model discovery

It provides Quantile-Quantile plots to visualize deviations between a model and data without binning.Read 5 Oct 2026 · johannesbuchner.github.io

Notable change

In version 5, Xspec priors use soft parameter limits instead of hard parameter limits, which the release notes flag as a potentially breaking change.Read 5 Oct 2026 · johannesbuchner.github.io

Parallel processing

MPI parallelisation can scale inference from laptops to computing clusters when mpi4py is installed.Read 5 Oct 2026 · johannesbuchner.github.io

Parameter estimation

It estimates parameters in arbitrary dimensions, finds best fits, computes error bars and marginal probability distributions, and supports MPI parallelisation.Read 5 Oct 2026 · johannesbuchner.github.io

Security and warranty

The repository publishes a GNU GPL license whose text disclaims warranties for the program.Read 5 Oct 2026 · github.com

Supported systems

BXA runs on operating systems supported by CIAO/Sherpa or HEASoft/Xspec, while release testing is stated to cover Ubuntu Linux only.Read 5 Oct 2026 · johannesbuchner.github.io

Xspec compatibility

When run from pyxspec, BXA provides chain FITS files compatible with Xspec/pyxspec MCMC features and error propagation tools.Read 5 Oct 2026 · johannesbuchner.github.io

Plans and prices

Every BXA plan and price →

Where Specifiction places it

• Astronomy Apps#12 of 357.9