# Change Log¶

## Version 16 (2020-05-28)¶

General

• Add the new ✨Early-Warning Alerts section to introduce early warning alerts as a public post-O3 technology demonstration. Early warning alerts are detections of binary neutron star merger candidates up to tens of seconds before merger. Starting on 2020-06-09 and lasting for one week, simulated early-warning alerts from replayed O3 LIGO/Virgo data will be publicly distributed at a rate of approximately once per day.

Observing Capabilities

• Note suspension of Observing Run 3 (O3) on March 27, 2020, due to the COVID-19 pandemic. When it becomes safe to resume normal activities, there may be a short period of additional O3 observations before an extended shutdown to prepare for the next observing run (O4). Updates will be posted in this document as they become available.

Alert Contents

• Add an example EarlyWarning GCN notice.

## Version 15 (2020-01-15)¶

Observing Capabilities

• Add sensitivity, detection rate, and localization accuracy statistics for O3 and O4 from the most recent arXiv submission of the LIGO/Virgo/KAGRA observing scenarios paper, arXiv:1304.0670. Add ranges for BBH and NSBH sources. Update O3 timeline and range schedule figures. Expect another update in the next few weeks incorporating O3a.

## Version 14 (2020-01-06)¶

Data Analysis

• Change FAR threshold due to the additional trials from the GRB coincidence search.

Alert Contents

• Add VOEvent documentation and examples for gravitational-wave events that are coincident with GRBs.

## Version 13 (2019-12-16)¶

Data Analysis

• Add a note that the oLIB search is not currently in operation.

Alert Contents

• Add a warning that VOEvent over anonymous VTP is the only GCN format and distribution method that is fully supported by LIGO/Virgo. In particular, LIGO/Virgo performs only limited quality control control checks for the textual “full format” and the binary format.

• In the VOEvent alert schema, add a name attribute to each <Group> tag so that parameter groups are recognized by the get_grouped_params() function from the voevent-parse package. For backwards compatibility, both the name attribute and the type attribute will be set to the same value.

The groups are now denoted as follows:

• <Group name="GW_SKYMAP" type="GW_SKYMAP"> for localization parameters

• <Group name="Classification" type="Classification"> for compact binary source classification parameters

• <Group name="Properties" type="Properties"> for compact binary source properties parameters

Additional Resources

• Add the Chirp mobile app for iOS and Android by Laser Labs.

## Version 12 (2019-10-24)¶

Observing Capabilities

• Update ranges and rates based on up-to-date O3 analysis. Add BBH and NSBH ranges. Update range and observing schedule figures.

• Generalize the definition of the range so that it is unambiguous at high redshift. It is now defined as in arXiv:1709.08079.

• Add the end date of Observing Run 3 (O3) on 2020-04-30.

Data Analysis

• Document the false alarm rate threshold for public alerts.

Alert Contents

• Remove the documentation for the Fluence parameter from burst alerts because it is not currently present in the VOEvents.

• Update the list of pipeline names that can appear in GCN Notices.

Additional Resources

• Created a new section for additional and contributed tools. The ligo.skymap and Aladin pages have been moved into this section.

• Add instructions for cross-matching sky localizations with galaxy catalogs in Aladin Desktop.

• Add the unofficial iOS Gravitational Wave Events app.

## Version 11 (2019-09-15)¶

Data Analysis

• Update the documentation about superevents describing the criteria by which the preferred event is selected. For CBC events, events with three detectors are preferred over two detectors, and events with two detectors are preferred over events with one detector.

Alert Contents

• Add references to the HEALPix paper (Górski et al. 2005, doi:10.1086/427976).

• Add version number suffixes to sky map FITS filenames in GCN notices to distinguish between different sky maps with the same filename. For example, the first file with the name bayestar.fits.gz will be referred to as bayestar.fits.gz,0, then the next will be bayestar.fits.gz,1, and so on. The filename with no version suffix always points to the most recent version.

Sample Code

• Add attribution for a HEALPix illustration that was reproduced from https://healpix.jpl.nasa.gov.

• Fix the example image for hp.mollview(), which was distorted due to a file conversion issue.

• Add section on sky map visualization and credible regions in Aladin.

## Version 10 (2019-07-31)¶

Data Analysis

• Add a more detailed description of the RAVEN pipeline. Previously just mentioned types of searches but now has information on external experiments, coincident searches, and coincident false alarm rates.

• Fixed PyCBC Live reference.

Alert Contents

• Changed the data type of the UNIQ column of the multi-order sky map format from an unsigned integer to a signed integer as specified by the MOC-in-FITS standard.

This will improve interoperability with the mrdfits function from the IDL Astronomy User’s Library and the fv FITS Viewer from FTOOLS, both of which were reported to have problems with the old unsigned integer column. It will also make it simpler to work with Numpy indexing operations, since Numpy uses a signed integer type for indexing.

This change will go into effect in the LIGO/Virgo low-latency alert system on 2019-08-06.

Users of ligo.skymap should update to version 0.1.8 or newer because older versions will be unable to read old files with unsigned UNIQ columns. The new version of ligo.skymap can read files with either signed or unsigned UNIQ columns.

## Version 9 (2019-06-13)¶

General

Data Analysis

• Renamed this section from “Procedures” to “Data Analysis” and reordered its subsections to better reflect the chronological order of the steps of the analysis.

Sample Code

• Add tutorial on working with multi-resolution sky maps.

• Add sample code to test whether a sky position is in the 90% credible region.

• Add sample code to find the area of the 90% credible region.

## Version 8 (2019-05-22)¶

Alert Contents

• Describe the two localization formats, the official *.fits.gz HEALPix-in-FITS format and the experimental multi-resolution HEALPix *.multiorder.fits format.

Effective 2019-05-28, the multi-resolution file suffix will be renamed from *.fits to *.multiorder.fits. The old *.fits suffix had caused confusion because the multi-resolution format is not the same as the *.fits.gz files without gzip compression.

The multi-resolution format is currently recommended only for advanced users. Tutorials and sample code will soon be included in an upcoming version of the User Guide.

• Update the description of the HasNS property in the sample GCN Notices. Previously, it was defined as the probability that at least one object in the binary has a mass that is less than 2.83 solar masses. Now, for consistency with the source classification definitions, it is defined as the probability that at least one object in the binary has a mass that is less than 3 solar masses.

• Add some shading to the source classification diagram to make it clear that the definitions of the source classes are symmetric under exchange of the component masses, but that by convention the component masses are defined such that $$m_1 \geq m_2$$.

## Version 7.1 (2019-03-02)¶

• Remove the warning on the front page about significant changes to this document occurring before the start of O3.

## Version 7 (2019-03-02)¶

Observing Capabilities

• Record the official start of O3.

Procedures

• Add Gravitational Wave/High Energy Neutrino search to the list of multi-messenger search pipelines.

Sample Code

• Add instructions for installing required packages using the Anaconda Python distribution.

## Version 6 (2019-03-08)¶

Alert Contents

• Switch to the GW170817 Hanford-Livingston-Virgo localization for the example sky map.

## Version 5 (2019-03-01)¶

Alert Contents

• Add a human-readable description to the Pkt_Ser_Num parameter.

• Add <EventIVORN cite="supersedes"> elements to the sample Initial and Update notices in order to cite all prior VOEvents. GraceDB already includes this metadata, but it was missing from the examples.

• Add MassGap classification for compact binary mergers.

## Version 4 (2019-02-15)¶

General

Getting Started Checklist

• Update links for OpenLVEM enrollment instructions.

Observing Capabilities

• Update planned dates for Engineering Run 14 (ER14; starts 2019-03-04) and Observing Run 3 (O3; starts 2019-04-01).

• Add Live Status section, listing some public web pages that provide real-time detector status.

Sample Code

• Update the example GCN notice handler so that it does not fail if the notice is missing a sky map, because as we have specified them, LVC_RETRACTION notices never contain sky maps and LVC_PRELIMINARY notices may or may not contain sky maps.

• When building the documentation, test all of the sample code automatically.

## Version 3 (2019-02-13)¶

Alert Contents

• Remove the skymap_png parameter from the VOEVents. The sky map plots take longer to generate than the FITS files themselves, so they would have needlessly delayed the preliminary alerts.

• Change the IVORN prefix from ivo://gwnet/gcn_sender to ivo://gwnet/LVC, because GCN traditionally uses the text after the / to indicate the name of the mission, which most closely corresponds to “LVC,” short for “LIGO/Virgo Collaboration.” Note that this IVORN is used for historical purposes and continuity with the GCN notice format used in O1 and O2, and is likely to change in the future with the commissioning of additional gravitational-wave facilities.

• Retraction notices now get a separate GCN notice packet type, LVC_RETRACTION=164. The Retraction parameter has been removed from the <What> section.

## Version 2 (2018-12-13)¶

Alert Contents

• Removed the Vetted parameter from GCN Notices. It was intended to indicate whether the event had passed human vetting. However, it was redundant because by definition Preliminary events have not been vetted and all Initial and Update alerts have been vetted.

• The type of the Retraction parameter in the GCN Notices was changed from a string (false or true) to an integer (0 or 1) for consistency with other flag-like parameters.

• Remove the units attribute from parameters that are not numbers.

Sample Code

• GCN has now begun publicly broadcasting sample LIGO/Virgo GCN Notices. Updated the sample code accordingly with instructions for receiving live sample notices.

## Version 1 (2018-11-27)¶

Getting Started Checklist

• Updated instructions for joining the OpenLVEM Community.

Observing Capabilities

• Changed the expected number of BNS events in O3 from 1-50, as stated in the latest version of the Living Review, to 1-10 events, as stated in the more recent rates presentation.

Alert Contents

• In the example VOEvents, moved the Classification and Inference quantities from the <Why> section to the <What> section so that they validate against the VOEvent 2.0 schema.