Event Portal Usage Notes
The Event Portal provides an interface for finding strain data for events discovered with LIGO and Virgo.
Releases are collections of events. You can see a listing of available releases on the Release List page.
The GWTC (Gravitational Wave Transient Catalog) is a cumulative set of gravitational wave transients maintained by the LIGO/Virgo/KAGRA collaboration. The GWTC contains events from multiple data releases; for details, see documentation for individual releases.
Some events may be listed in the database with multiple version numbers. Different versions of the same astrophysical event may differ in one or more of the following:
- Different versions of calibration applied to the associated strain data
- Different cleaning techniques applied to the associated strain data
- Different analysis results
- Different publications
You can see all versions for a given event by entering the event's name in the Name Query Form.
The information on the Event Portal can be accessed through a JSON API. For more details, read the API Documentation page.
The version history of the Event Portal is archived in "Event Portal Snapshots", available in a zenodo dataset.
Information for individual events
Individual event views (e.g. GW150914 v3 ) provide information about a given event entry. This includes:
- Documentation: Documentation or reference to give context for a given event.
- GPS: End time or merger time of the event in GPS seconds.
- GraceDB: If available, a link to the corresponding entry in GraceDB, a database of preliminary results from low-latency searches.
- GCN: Links to associated GCN notices and circulars, used to communicate low-latency results at the time of discovery.
- Timeline: Link to segment and data quality information
- Notes: Technical notes. In many cases, this gives details about which version of strain is included in this version.
Available strain data for the event are displayed on cards, with one card for each detector with data available. Detectors do not run at all times, so any given event may not have data from all detectors.
Each card includes:
- The detector code (H1 for Hanford, L1 for Livingston, V1 for Virgo, G1 for GEO)
- A time-frequency plot showing the Q-transform of a small segment of data, centered on the merger time. These are produced using the Q-transform method in gwpy. You can make similar plots using the Quickview notebook.
- Data download links for strain data available in different durations (typically 32 seconds and 4096 seconds), different sampling frequencies (16384 Hz or 4096 Hz) and different file formats (GW frame files, HDF5, or ASCII text).
Some event parameters, such as masses, spins, and SNRs, are available for many events.
- Standard parameter estimation names and definitions can be found at this link.
- Parameters may come from either search pipelines or parameter estimation pipelines.
- False alarm rates and P_astro (when available) are provided only by search pipelines, and SNRs may be provided either by a search or a parameter estimation pipeline. Most other parameters are calculated by parameter estimation pipelines.
- Single Event Views show parameters organized by pipeline and/or pipeline configurations (e.g. multiple waveform families).
- Event List Views show parameters from a sub-set of the available pipelines and configurations. This may be a search pipeline, a parameter estimation pipeline, or one of each. Parameter sets displayed in the Event List view are marked as "Default PE" or "Default SEARCH" in the Single Event View.
- On an Event List View, the lowest FAR and highest p_astro value available for a given version of an event are displayed. For other parameters, preference is given to values with the label "Default PE". For those events that do not have parameter estimation results (typically the case for the marginal catalog event list views), the best search pipeline SNR is displayed when available.
- The table on the Event List View supports sorting on any of the columns by clicking on the column header. The sort feature has three states that cycle through as you click on a particular column header. The first state sorts the table on the selected column in "ascending" order (first row having smallest value), and will have up arrow in the column header; the second state sorts the table in "descending" order (first row having the largest value), and will have a down arrow in the column header; the third state returns the table to its original ordering of earliest GPS time to latest GPS time for the events listed. Clicking on any column header cycles through these three states depending on the number of times you click.
- In most cases, parameter estimation values are derived directly from publicly available PE samples. These samples are linked from the Single Event Views.
- The "date added" field corresponds to the date information was added to our database, which is typically not the same as the release date.
- The Event Portal was created around December of 2019, so events released earlier may include a "date added" close to this date, rather than the actual detection or release date.
- See documentation for individual releases for more details.
A number of notes about GWOSC event releases and their use may be seen on the event release technical details page.
Image on event portal home page is adopted from art by Aurore Simonnet at Sonoma State.