GWTC-3 Data Release Documentation

Description

This data release is described in: GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run. GWTC-3 is a cumulative catalog describing all the gravitational-wave transients found in observing run O3b. This page provides documentation for the confident and marginal events found in O3b. Comparable information for earlier event releases may be found by following the links for GWTC-1, GWTC-2, and GWTC-2.1 (where the latest information for O1, O2, and O3a may be found).

Here we provide the strain and data quality for GWTC-3-confident events and the GWTC-3-marginal candidates described in Tables I and II of the GWTC-3 catalog paper. Search results for FAR, SNR and P_astro are provided for all events and marginal candidates.

Table I of the GWTC-3 catalog paper lists 35 probable events that were found by at least one search algorithm with probability of astrophysical origin assuming a compact binary coalescence source (P_astro) greater than 0.5. The strain, segments, search results and parameter estimation values with corresponding 90% credible intervals are listed in GWTC-3-confident. For candidates identified by the minimally modeled cWB search analysis, we additionally require that a candidate be found by one of the templated-based analysis with P_astro > 0.1, since cWB can detect many types of signal, and additional verification is needed for the assumption of a compact binary coalescence source.

Table II in the GWTC-3 catalog paper presents 7 marginal candidates with P_astro that does not satisfy the criteria for Table I, but were found with a FAR below a threshold of 2 per year in at least one analysis. The strain, segments and search results for these 7 are listed in GWTC-3-marginal. The GW prefix is omitted when a plausible instrumental origin has been identified.

Displayed in the "Event List Views" for both the GWTC-3-confident and GWTC-3-marginal are the lowest false alarm rate and highest P_astro value taken across all search pipelines. The SNR value displayed is taken from the default PE result, or in the cases where no PE results are provided, the highest SNR from the search pipelines. Additional results can be found by clicking each event. See Event Portal Usage Notes for more details.

In addition, the paper identifies 1041 subthreshold candidates with a FAR less than 2 per day in any search pipeline. Data products associated with these subthreshold candidates are available in zenodo, as listed in the Data Products and Publications section below.

Strain Data

Strain data for O3b confident events and O3b marginal candidates are available through the Event Portal. These events are also included in a cumulative list of all confident GWTC events published to date.

Associated strain data are from the Advanced LIGO and Advanced Virgo O3b observing run, between 1 November 2019 15:00 UTC and 27 March 2020 17:00 UTC.

Click on any event, and then select a GWF, HDF, or TXT file to download strain data.

Parameter Estimation

Parameter estimation values with 90% credible intervals for some parameters are displayed in the Event Portal. The samples for each event used to produce these values for each event in GWTC-3-confident are available in Zenodo.

Parameter names are defined using standard PESummary parameter names. Note that parameter estimation results reported in this catalog include the original versions published on arXiv along with a second (updated) set of values first publisched in the revised version on October 23, 2023arXiv.

Low-Latency Alerts

Some events in the release triggered low-latency alerts, and were advertised through GCN. Any available low-latency information is linked from each event page. However, for events that did not trigger low-latency alerts, these links will yield "page not found." See the O3 Public Alerts Page for a complete list.

Data Products and Publications

Special Cases

200214_224526

This marginal candidate was identified only by the cWB search (and not by any template-based search analysis) with a P_astro greater that 0.5, while also satisfying the FAR threshold of below 2 per year. The cWB assumes a CBC source, however cWB can detect many types of signal, and so this assumption is not necessarily valid. In this case, we do not have confirmation that the candidate signal is CBC-like. As with 200121_031748 and 200219_201407 listed in GWTC-3-marginal, it is likely to be caused by instrumental artifacts.

Notes on Strain Data

Data files containing calibrated strain are available for 4096 seconds centered on each event. Note that LIGO and Virgo data contain a number of instrumental artifacts, many of which are noted on the strain data notes page.

Data are a calibrated strain time series sampled at 16384 Hz. Also provided is a copy of these data down-sampled to 4096 Hz. The down-sampled data were obtained using the scipy 'decimate' method. The anti-aliasing filter introduces errors up to a few percent in magnitude and a few milli-radians across the band, with larger errors close to the Nyquist frequency. 

from scipy.signal import decimate
data4seg = decimate(data16seg, 4, zero_phase=True)

Advanced LIGO and Virgo strain data are not calibrated below 10 Hz, as noted on the strain data notes page.

Event Names

GWTC-3 event names are formatted as UTC date and time when the event appears in the data (GWYYMMDD_HHMMSS). The GW prefix is omitted when there is an identified plausible instrumental origin.

Reading Files

Channel names found inside GWF files
4096 Hz Sampling Rate 16384 Hz Sampling Rate
{ifo}:GWOSC-4KHZ_R1_STRAIN {ifo}:GWOSC-16KHZ_R1_STRAIN
{ifo}:GWOSC-4KHZ_R1_DQMASK {ifo}:GWOSC-16KHZ_R1_DQMASK
{ifo}:GWOSC-4KHZ_R1_INJMASK {ifo}:GWOSC-16KHZ_R1_INJMASK

Where {ifo} = H1, L1, or V1

Other releases of O3b strain data

Data products for the same time period from different releases may have small differences due to different versions of calibration, data cleaning, and/or differences in how the down-sampling was applied to produce 4096 Hz files. Data quality segment information has also been updated, including times when low amplitude continuous wave injections were active.

Segments / Data Quality

Data quality categories are as defined in the event technical notes page. Continuous Wave injections (CW) are present during most events at a very low amplitude, and do not interfere with transient detection.

Data availability, data quality, and hardware injection segments are available:

  • In the data files, through bit masks with these bitmask definitions. The bitmask definitions are consistent across all events in this catalog.
  • Segment information for each event is available on individual event pages. Select an event from the first column on either the GWTC-3-confident Event List or the GWTC-3-marginal Candidate List page, then click on "Timeline: Query for Segments" found in the top left hand box.

Hardware Injections

In some cases, simulated signals known as O3 hardware injections may be present in data files. Segment lists of hardware injections are available for each event.

Calibration Versions

The following channels and frame types were used from the original GWF frame files to package GWOSC public strain data. The 16 kHz strain vector exactly matches the source channels for times where DATA are available: 

All events in GWTC-3:
{   'H1':('H1:DCS-CALIB_STRAIN_CLEAN_SUB60HZ_C01', 'H1_HOFT_CLEAN_SUB60HZ_C01'), 
    'L1':('L1:DCS-CALIB_STRAIN_CLEAN_SUB60HZ_C01', 'L1_HOFT_CLEAN_SUB60HZ_C01'), 
    'V1':('V1:Hrec_hoft_16384Hz', 'V1Online),

The DOI for this page is https://doi.org/10.7935/b024-1886

Release Notes

  • First release: November 7, 2021
  • Updated SNR, FAR and P_astro selections in Event List View: August 16, 2022
  • Added note regarding updated parameter estimation: Nov 1, 2023