2-OGC: Open Gravitational-wave Catalog of binary mergers from analysis of public Advanced LIGO and Virgo data

**Alexander H. Nitz^{1, 2}, Thomas Dent³, Gareth S. Davies³,Sumit Kumar^{1, 2}, Collin D. Capano^{1, 2}, Ian Harry^{4, 5}, Simone Mozzon⁴, Laura Nuttall⁴, Andrew Lundgren⁴, and Marton Tapai⁶ **

_{1. Albert-Einstein-Institut, Max-Planck-Institut for Gravitationsphysik, D-30167 Hannover, Germany}
_{2. Leibniz Universitat Hannover, D-30167 Hannover, Germany}
_{3. Instituto Galego de F´ısica de Altas Enerx´ıas, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain}
_{4. University of Portsmouth, Portsmouth, PO1 3FX, United Kingdom}
_{5. Kavli Institute of Theoretical Physics, UC Santa Barbara, CA}
_{6. Department of Experimental Physics, University of Szeged, Szeged, 6720 D´om t´er 9., Hungary}

Introduction

We present the second Open Gravitational-wave Catalog (2-OGC) of compact-binary coalescences, obtained from the complete set of public data from Advanced LIGO's first and second observing runs. For the first time we also search public data from the Virgo observatory. Our analysis is based upon updated methods to improve detection of compact binary mergers by incorporating corrections for short time variations in the detectors' noise power spectral density and instantaneous network sensitivity. We identify a population of 14 binary black hole mergers along with the GW170817 binary neutron star merger. We confirm the binary black hole merger observations of GW170121, GW170304, and GW170727. We also report GW151205, a new marginal binary black hole merger during the first observing run. No other individually significant binary neutron star candidates are found, nor did we observe any significant neutron star--black hole candidates. We make available our comprehensive catalog of events, including the sub-threshold population of candidates to enable deeper follow-up as our understanding of the underlying populations evolves.

The catalog is stored in the file '2-OGC.hdf'. There are a variety of tools to access hdf files from numerous computing languages. Here we will focus on access through python and h5py.

Analysis Details

Details of the analysis are available in this preprint paper and the configuration files needed to create the analysis workflows are provided in the search_configs directory.

Accessing the Catalog: 2-OGC.hdf

There are two datasets within the file, /complete and /bbh. The complete set is the full dataset from our analysis. The bbh set includes BBH candidates from the bbh-region targeted analysis. See the 2-OGC paper for additional information.

import h5py

catalog = h5py.File('./2-OGC.hdf', 'r')

# Get a numpy structured array of the candidate event properties.
all_candidates = catalog['complete']
bbh_candidates = catalog['bbh']

# Accessing a column by name
ranking_values = all_candidates['stat']

# Selecting parts of the catalog
region = all_candidates['mass1'] + all_candidates['mass2'] < 4
lowmass_candidates = all_candidates[region]

File format

Both datasets are structured arrays which have the following named columns. Some of these columns give information specific to either the LIGO Hanford, LIGO Livingston or Virgo detectors. Where this is the case, the name of the column is prefixed with either a H1, L1, or 'V1'.

Key	Description
name	The designation of the candidate event. This is of the form 150812+12:23:04UTC.
far	The rate of false alarms with a ranking statistic as large or larger than this event. The unit is yr^-1.
stat	The value of the ranking statistic for this candidate event.
mass1	The component mass of one compact object in the template waveform which found this candidate. Units in detector frame solar masses.
mass2	The component mass of the template waveform which found this candidate. Units in detector frame solar masses.
spin1z	The dimensionless spin of one of the compact objects for the template waveform which found this candidate.
spin2z	The dimensionless spin of one of the compact objects for the template waveform which found this candidate.
{H1/L1/V1}_end_time	The time in GPS seconds when a fiducial point in the signal passes throught the detector. Typically this is near the time of merger.
{H1/L1/V1}_snr	The amplitude of the complex matched filter signal-to-noise observed.
{H1/L1/V1}_coa_phase	The phase (angle) of the complex matched filter signal-to-noise observed.
{H1/L1/V1}_reduced_chisq	Value of the signal consistency test defined in this paper. This is not calculated for all candidate events. In this case a value of 0 is substituted.
{H1/L1/V1}_sg_chisq	Value of the signal consistency test defined in this paper. This is not calculated for all candidate events. In this case a value of 1 is substituted.
{H1/L1/V1}_sigmasq	The integral of the template waveform divided by the power spectral density.

The /bbh dataset also has the following additional column.

Key	Description
pastro	The probability that this BBH candidate is of astrophysical origin.

License and Citation

This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 United States License.

We encourage use of these data in derivative works. If you use the material provided here, please cite the paper using the reference:

@article{Nitz:2019hdf,
      author         = "Nitz, Alexander H. and Dent, Thomas and Davies, Gareth S.
                        and Kumar, Sumit and Capano, Collin D. and Harry, Ian and
                        Mozzon, Simone and Nuttall, Laura and Lundgren, Andrew and
                        Tápai, Marton",
      title          = "{2-OGC: Open Gravitational-wave Catalog of binary mergers
                        from analysis of public Advanced LIGO and Virgo data}",
      year           = "2019",
      eprint         = "1910.05331",
      archivePrefix  = "arXiv",
      primaryClass   = "astro-ph.HE",
      SLACcitation   = "%%CITATION = ARXIV:1910.05331;%%"
}

Acknowledgments

We acknowledge the Max Planck Gesellschaft and the Atlas cluster computing team at AEI Hannover for support. Research supported by Maria de Maeztu Unit of Excellence MDM-2016-0692. This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. This research has made use of data, software and/or web tools obtained from the Gravitational Wave Open Science Center (https://www.gw-openscience.org), a service of LIGO Laboratory, the LIGO Scientific Collaboration and the Virgo Collaboration. LIGO is funded by the U.S. National Science Foundation. Virgo is funded by the French Centre National de Recherche Scientifique (CNRS), the Italian Istituto Nazionale della Fisica Nucleare (INFN) and the Dutch Nikhef, with contributions by Polish and Hungarian institutes.

cdcapano/2-ogc