DOI: 10.5281/zenodo.15540557
title: IAS O3b catalog of binary black hole mergers

description: This is a release of parameter estimation results from the events reported by the IAS-O3b search described in "New binary black hole mergers in the LIGO-Virgo O3b data" (Mehta et al. 2025). We provide posterior samples for all the events identified therein that have probability of astrophysical origin greater than 0.5. This amounts to 23 events, including 6 that had not been reported previously.

A summary of this dataset is also being uploaded to the Gravitational Wave Open Science Center's community catalogs.

Data Products

Posterior samples



weights: Importance-sampling weight of each sample.

f_ref: Frequency of the (l, |m|) = (2, 2) mode at which the initial condition is specified (Hz).

m1: Detector-frame primary mass (solar masses).

m2: Detector-frame secondary mass (solar masses).

iota: Inclination angle (rad).

s1x: Dimensionless spin of the primary in the x direction.

s1y: Dimensionless spin of the primary in the y direction.

s1z: Dimensionless spin of the primary in the z direction.

s1x_n: Dimensionless spin of the primary in the x_n direction.

s1y_n: Dimensionless spin of the primary in the y_n direction.

s2x: Dimensionless spin of the secondary in the x direction.

s2y: Dimensionless spin of the secondary in the y direction.

s2x_n: Dimensionless spin of the secondary in the x_n direction.

s2y_n: Dimensionless spin of the secondary in the y_n direction.

s2z: Dimensionless spin of the secondary in the z direction.

d_luminosity: Luminosity distance (Mpc).

ra: Right ascension (rad).

dec: Declination (rad).

phi_ref: Orbital phase at the reference frequency (rad).

psi: Polarization angle (rad).

t_geocenter: Arrival time at the center of Earth relative to tgps (s).

mchirp: Detector-frame chirp mass (solar masses).

chieff: Effective spin.

mtot: Detector-frame total mass (solar masses).

redshift: Cosmological redshift.

m1_source: Source-frame primary mass (solar masses).

m2_source: Source-frame secondary mass (solar masses).

mchirp_source: Source-frame chirp mass (solar masses).

mtot_source: Source-frame total mass (solar masses).

lnl: Log-likelihood.




Coordinate systems:



(x, y, z) are the standard LAL coordinates, where x is along the separation of the two objects at f_ref, and z is along the orbital angular momentum, see https://lscsoft.docs.ligo.org/lalsuite/lalsimulation/group__lalsimulation__inference.html

(x_n, y_n) are rotated with respect to (x, y) by an angle phi_ref; thus, these axes are defined in terms of the orbital angular momentum and the line of sight without regard to the orbital separation vector.



Priors: Events are analyzed under two different priors (here referred to as "IAS" and "LVK"). These only differ in the spin distribution (the IAS prior is uniform in effective spin, the LVK prior is uniform in spin magnitudes and isotropic in spin orientations). In both cases, the prior for the masses is uniform in detector-frame component masses and uniform in comoving volume-time.

Software: Parameter inferences were done using cogwheel (Roulet et al. 2022, 2024), coupled to the stochastic samplers Nautilus (Lange 2023).

Strain data

For each event, the strain data is provided in npz format, see the usage demo for how to load it. For one event, glitch has been inpainted. The file inpaint_times.json contains the times at which this event and detector was inpainted, measured in seconds from the GPS time of the event.

Events metadata

The following summary information from the search pipeline is provided for each event in events_metadata.json:



ifar_yr: Inverse false-alarm rate in each bank (y).

ifar_global_yr: Inverse false-alarm rate combined over all the banks (y).

pastro: Probability of astrophysical origin.

gracedb_id: If available, corresponding entry in GraceDB.

tgps: GPS time.

snr: Signal-to-noise ratio achieved by the trigger in the search, in the Hanford-Livingston network.


GWOSC upload

A summary of this dataset is being uploaded to the Gravitational Wave Open Science Center's community catalogs. This summary is contained in a file ias-o3b.json, which we provide along with a jupyter notebook prepare_json.ipynb used to generate it.

Authors

This release was put together by Ajit Kumar Mehta and Javier Roulet.

The IAS-O3b search was carried out by Ajit Kumar Mehta, Seth Olsen, Digvijay Wadekar, Javier Roulet, Tejaswi Venumadhav, Jonathan Mushkin, Barak Zackay, and Matias Zaldarriaga.

Acknowledgements

This research has made use of data or software obtained from the Gravitational Wave Open Science Center (gwosc.org), a service of the LIGO Scientific Collaboration, the Virgo Collaboration, and KAGRA. This material is based upon work supported by NSF's LIGO Laboratory which is a major facility fully funded by the National Science Foundation, as well as the Science and Technology Facilities Council (STFC) of the United Kingdom, the Max-Planck-Society (MPS), and the State of Niedersachsen/Germany for support of the construction of Advanced LIGO and construction and operation of the GEO600 detector. Additional support for Advanced LIGO was provided by the Australian Research Council. Virgo is funded, through the European Gravitational Observatory (EGO), by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale di Fisica Nucleare (INFN) and the Dutch Nikhef, with contributions by institutions from Belgium, Germany, Greece, Hungary, Ireland, Japan, Monaco, Poland, Portugal, Spain. KAGRA is supported by Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan Society for the Promotion of Science (JSPS) in Japan; National Research Foundation (NRF) and Ministry of Science and ICT (MSIT) in Korea; Academia Sinica (AS) and National Science and Technology Council (NSTC) in Taiwan.