ACME - Parameter Estimation in Gravitational-Wave Astronomy with Bilby

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Giancarlo Cella (INFN Pisa)
Description

This tutorial focuses on parameter estimation for gravitational-wave signals using Bilby. It introduces the full analysis workflow, from the definition of signal models to the interpretation of posterior distributions, with an emphasis on realistic data conditions and practical implementation. Participants work with the bilby.gw framework to analyze signals from compact binary coalescences. The tutorial covers waveform modeling based on the Post-Newtonian approximation and Effective One Body formalism, as well as detector noise characterization and the role of calibration and assumptions about stationarity and Gaussianity. Particular attention is given to parameter degeneracies and to the interpretation of uncertainties. Through guided exercises, participants perform complete inference runs, explore the impact of prior choices, and test the robustness of results under controlled variations of the analysis setup. Additional topics include injection studies and extensions toward more complex inference scenarios. The goal is to provide a solid and practical understanding of gravitational-wave parameter estimation and to enable participants to carry out and critically assess their own analyses.


  • 09:30 Welcome, ACME introduction, environment check.
  • 09:45 Lecture 1 — from the signal to the posterior: likelihood, PN/EOB/phenomenological waveforms, the map of degeneracies.
  • 10:30 Lab 1 — reference parameter-estimation run on a GW150914-like injection (HLV network).
  • 11:15–11:30 Break.
  • 11:30 Lecture 2 — noise, calibration and priors.
  • 12:00 Lab 2 — controlled variations: waveform model, priors, PSD, calibration, glitch, GW150914 open data.
  • 12:55 Lab 3 — injection studies and PP tests.
  • 13:15 Wrap-up, extensions and closing discussion.

Note: times are indicative.

Preparation. Exercises are Python scripts (no notebooks). Please install the environment before the session (uv, Python 3.11, bilby==2.8.0, lalsuite, gwpy, dynesty; on Windows use WSL) and run 00_check_env.py; instructions and scripts will be attached to this page. Introductory material: https://indico.global/event/17359/ and https://indico.global/event/18335/. The connection link is sent by email to registered participants.


    • 1
      Welcome, ACME introduction, environment check

      ACME project slides; check of the Python environment with 00_check_env.py.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 2
      Lecture 1: from the signal to the posterior

      Likelihood for Gaussian stationary noise; post-Newtonian, Effective One Body and phenomenological waveforms; distance-inclination and mass ratio-spin degeneracies; distance/phase marginalisation and relative binning.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 3
      Lab 1: reference parameter-estimation run

      01_pe_reference.py: GW150914-like injection in the H1-L1-V1 network, inference with dynesty; reading corner plots, credible intervals, SNR.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 11:15
      Break
    • 4
      Lecture 2: noise, calibration and priors

      PSD estimation, stationarity and Gaussianity, glitches; calibration model; distance, mass and spin priors and their effect on the posterior.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 5
      Lab 2: controlled variations

      02_variations.py: waveform model, priors, PSD, calibration, glitch, GW150914 open data, each compared with the reference run.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 6
      Lab 3: injection studies and PP tests

      03_injection_study.py: PP plots and Kolmogorov-Smirnov tests on precomputed injection campaigns; how to launch one.

      Speaker: Giancarlo Cella (INFN Pisa)
    • 7
      Wrap-up, extensions and closing discussion

      Precession and higher modes, binary neutron stars, bilby_pipe; next tutorial on 14 December; ticketing system and survey.

      Speaker: Giancarlo Cella (INFN Pisa)