Gallery: Black hole-neutron star GW230529

This gallery example evolves a non-spinning black hole-neutron star merger with chirp mass and effective spin chosen to be consistent with GW230529. The setup is described in Matur et al. (2026).

The hydrodynamics are evolved with IllinoisGRMHD, while the spacetime is evolved with ML_CCZ4 within McLachlan. Initial data were generated with FUKA/Kadath.

Simulation details

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Physical setup

Masses	The ADM masses are 3.6 M⊙ for the BH, and 1.4 M⊙ for the NS.
Mass ratio	q = 2.57
Chirp mass	1.91 M⊙
Effective spin	χeff = 0, with both stars non-spinning.
Initial separation	45 km (about 1.5 orbits before merger)
Initial angular momentum	J0 = 17.04 M⊙2
Equation of state	Γ-law, with Γ = 2, K = 100.

Computational setup

Parameter file	bhns_gw230529.par
Thornlist	bhns.th
Initial data	bhns_gw230529_ID.tar.gz
Support scripts	scripts.tar.gz
Approx. memory	140 GB
Approx. runtime	30 hours on 2 nodes / 256 cores
Reference machine	DiRAC / COSMA8
Results	bhns-20250321.tar.gz (547 MB)
Last tested	2025-12-22

Supplementary data for this example are available on Zenodo.

Requirements

This example requires KadathImporter, KadathThorn, and the Boost library.

Compile and run

1. Download the thornlist:

   ./GetComponents --root BHNS http://einsteintoolkit.org/gallery/bhns/bhns.th

2. Enter the source tree:

   cd BHNS

3. Enable KadathImporter and KadathThorn in the thornlist:

   sed -i 's/^#DISABLED \(Fuka\/KadathImporter\|Fuka\/KadathThorn\)$/\1/' thornlists/bhns.th

4. Download the parameter file:

   curl -LO https://einsteintoolkit.org/gallery/bhns/bhns_gw230529.par

5. Generate the effective thornlist:

   ./utils/Scripts/MakeThornList -o bhns.th --master thornlists/bhns.th bhns_gw230529.par

6. Configure SimFactory:

   ./simfactory/bin/sim setup-silent

   You may need to edit ./simfactory/etc/defs.local.ini to set the allocation or machine-specific options.
7. Build:

   ./simfactory/bin/sim build --thornlist bhns.th

8. Unpack the initial-data archive with:

   tar -xzf bhns_gw230529_ID.tar.gz

   Replace /path/to/ in BHNS_ECC_RED.gam2.30.0.0.5.q0.388889.0.0.13.info with the exact path to gam2.polytrope.
9. Submit:

   ./simfactory/bin/sim submit bhns_gw230529 --parfile bhns_gw230529.par --cores=256 --num-threads=1 --walltime=30:00:00

Post-processing

Download and unpack the support scripts:

curl -LO https://einsteintoolkit.org/gallery/bhns/scripts.tar.gz
tar -xzf scripts.tar.gz

Example command for waveform plot generation:

python3 scripts/mp_Psi4_l2_m2_r500.00.py /full/path/to/output

Here /full/path/to/output is the simulation output directory containing the extracted waveform data.

Example command for rest-mass density movie generation:

Replace data_dir in scripts/rho_movie.py with the simulation output directory, then run:

./scripts/make_movie.sh

Here data_dir is the simulation output directory containing the 2D rest-mass density data.

Citation

If you make use of this parameter file, the example data, or the associated workflow, please cite the relevant Einstein Toolkit infrastructure and thorns, together with the BHNS example itself: BibTeX.

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