BLiSS is an open-source Python package for finding emission lines in spectra without telling the code where to look first. In other words: a real blind line-search algorithm — you only need your spectrum.

BLiSS was designed to simplify and speed up spectral analysis in X-ray astronomy. Instead of manually inspecting spectra, guessing candidate energies, and testing lines one by one, BLiSS performs an automatic search for statistically significant emission features and then cross-matches them with atomic transitions.

The package combines Gaussian line-profile fitting, statistical scoring, and database-based identification using XSTAR atomic data. It is especially useful when the continuum is complex, uncertain, or simply not the main focus of the analysis.

Although BLiSS was developed for X-ray spectra, the core idea is more general: if you have spectral data with uncertainties, BLiSS can help you search for emission features in a systematic and reproducible way.

Features

Blind emission-line search
Automatically searches spectra for statistically significant emission features.
No prior knowledge of line positions is required.
Automatic Gaussian fitting
Fits candidate features with Gaussian profiles.
Provides statistical ranking of all detected lines.
Continuum-independent workflow
Line searches can be performed without defining a global continuum model beforehand.
Atomic line identification
Cross-matches detected features with XSTAR atomic transitions.
Supports Doppler velocity constraints.
Flexible rebinning
Rebin spectra by instrumental resolution or target signal-to-noise ratio.
Null-spectrum evaluation
Reports five global Monte Carlo p-values based on synthetic null spectra.
Provides an additional empirical BLiSS score derived using Gaussian mixture modelling.
Reproducible analyses
Applies identical search criteria across large spectral samples.

Installation

Install BLiSS directly from PyPI:

pip install bliss-lib

or install the development version from GitHub:

git clone https://github.com/xragua/bliss.git
cd bliss
pip install -e .

Quick start

import bliss

# Import your spectrum

# Run the blind line search

# Inspect the detected candidates

Example notebooks are available in the notebooks/ directory:

https://github.com/xragua/BLiSS/tree/main/notebooks

Documentation

GitHub repository:

https://github.com/xragua/bliss

Latest releases:

https://github.com/xragua/bliss/releases

Requirements

Python 3.10 or newer
NumPy
SciPy
Pandas
Astropy
Matplotlib

These dependencies are installed automatically with BLiSS.

Citation

If you use BLiSS in your research, please cite:

@misc{abalo2026blindlinesearchsystem, title={Blind Line Search System: BLiSS}, author={Luis Abalo and Graciela Sanjurjo-Ferrín and Jessica Planelles-Villalva and José Joaquín Rodes-Roca and José Miguel Torrejón}, year={2026}, eprint={2607.07783}, archivePrefix={arXiv}, primaryClass={astro-ph.IM}, url={https://arxiv.org/abs/2607.07783}, }

Support

Bug reports, feature requests and suggestions are welcome through GitHub Issues:

https://github.com/xragua/bliss/issues

License

This project is distributed under the MIT License.

BLiSS — Blind Line Search System