Circulars Archive

Upon successful submission and distribution, a GCN Circular is assigned a number and stored permanently in the GCN Circulars archive. The archive lists links to the full text of every GCN Circular in reverse chronological order. The archive has a full-text search feature that you can use to find all Circulars that contain a phrase or keyword.

Go to GCN Circulars Archive

Searching the Archive

You can search the Circulars Archive by keywords or phrases in the subject, body, and submitter fields. By default, results will be returned in reverse chronological order, but you can also choose to sort the results by relevance. You can navigate through the search results using pagination controls and specify the number of results to display per page. By default, 100 results are displayed per page.

You can filter search results by submission date. Select the dropdown button labeled "Filter by date". From there, you can either select from a number of predefined time ranges (e.g., "Last Hour", "Last Day", etc.) or specify a custom date range, which can either be set as a start date, an end date, or both. All search filters can be cleared by clicking the 'x' button in the search bar.

Event View

The Circulars archive provides an Event View that allows users to view all Circulars associated with a particular astronomical event.

Each Circular is automatically assigned an event name derived from the subject (e.g. GRB 250109A, EP250109a). This assignment is done by matching against a regular expressions list.

The event name is listed in the JSON format version of Circulars. The first event name used in the subject is associated automatically, and all Circulars with the same event name are grouped. GCN moderators can associate multiple event names with a group, such that all Circulars with these event names will be listed in the same event group.

Adding events to the same group

GCN Team moderators can create or modify event groups. If you would like to suggest the creation or modification of an event group, submit a ticket via the contact form.

Searching by event name

In the Event View search bar, enter in an event name and it will take you to the associated event group. It will recognize regular expressions associated with the event name (e.g. GRB 123456A, GRB123456A, 123456A).

Linking to an event name or event group

To save a direct link to all Circulars assocaited with a particular event name or event group, you can point to any event name in that group, e.g. `https://gcn.nasa.gov/circulars/group/[event_name]'.

Advanced Search

The advanced search feature allows for searching keywords in a specific field of the circular. The search feature uses the Lucene query syntax to specify the field and search term.

Searching by Field

Searches can be performed by specifying the field and search term. The syntax for this is field:"search term". For example, to search for circulars with the word 'Swift' in the subject field, the query would be subject:"Swift".

The following fields are supported: subject, body, and submitter.

By default, a query that does not contain the advanced search syntax will attempt to match the query against all 3 fields. For example, the query Swift will match any circular that contains the word 'Swift' in the subject, body, or submitter fields, whereas the query subject:"Swift" will only match circulars where the subject contains the word 'Swift'.

Compound Queries

These separate field queries can be combined using additional keywords to form compound queries. The following boolean keywords are supported:

AND/&&: The AND/&& operator requires that both conditions are met. For example, subject:"Swift" AND body:"GRB" will match circulars where the subject contains 'Swift' and the body contains 'GRB'.
OR/||: The OR/|| operator requires that at least one condition is met. For example, subject:"Swift" OR body:"GRB" will match circulars where the subject contains 'Swift' or the body contains 'GRB'.
NOT/!: The NOT/! operator requires that the condition is not met and is commonly used with the AND/&& operator. For example, subject:"LIGO" AND NOT body:"GRB" will match circulars where the subject contains 'LIGO' and the body does not contain 'GRB'.

By default, the AND operator is used if no operator is specified. For example, subject:"Swift" body:"GRB" is equivalent to subject:"Swift" AND body:"GRB".

It is also possible to combine these operator keywords to form more complex queries. For example, subject:"Swift" AND (body:"GRB" OR body:"Gamma-ray burst") will match circulars where the subject contains 'Swift' and the body contains either 'GRB' or 'Gamma-ray burst'.

Using one of these operators without an additional field query will result in an error. For example, subject:"Swift" AND will raise an error. For queries that do not adhere to the advanced search syntax, GCN will fall back onto a more basic search method that matches the query against all fields with a warning message.

Reserved Characters

There are a number of reserved characters that have special meaning in the advanced search syntax. These characters must be escaped using a backslash (\) to be treated as a literal character. Including these characters in a query without escaping them will raise an error.The reserved characters are: +, -, =, &&, ||, >, <, !, (, ), {, }, [, ], ^, ", ~, *, ?, :, /, \.

Examples

Swift: Matches circulars where the subject, body, or submitter contains 'Swift'.
subject:"Swift": Matches circulars where the subject contains 'Swift'.
body:"Swift": Matches circulars where the body contains 'Swift'.
subject:"Swift" AND body:"GRB": Matches circulars where the subject contains 'Swift' and the body contains 'GRB'.
subject:"Swift" OR body:"GRB": Matches circulars where the subject contains 'Swift' or the body contains 'GRB'.
subject:"Swift" AND (body:"GRB" OR body:"Gamma-ray burst"): Matches circulars where the subject contains 'Swift' and the body contains either 'GRB' or 'Gamma-ray burst'.
subject:"LIGO" AND NOT body:"GRB": Matches circulars where the subject contains 'LIGO' and the body does not contain 'GRB'.

Citing GCN Circulars

The SAO/NASA Astrophysics Data System (ADS) ingests and indexes all GCN Circulars. You can use ADS to get bibliographic records for GCN Circulars to cite them in a publication.

When you are viewing a GCN Circular in the archive, you can click the "Cite (ADS)" button to go to the ADS entry for that Circular. Note that ADS entries are updated every Monday at 08:00 UTC, so the button may be disabled for the most recent GCN Circulars.

GCN Viewer

The GCN Viewer also automatically ingests and parses GCN Circulars, sorting them by astronomical event, and associates them with their GCN Notices.

Migration of Archive from GCN Classic

The GCN Circulars archive was migrated from the GCN Classic Circulars archive page on April 17, 2023. The new GCN Circulars archive on this site is the authoritative record of all past Circulars and is updated in real time with new Circulars. The old GCN Classic Circulars archive page is preserved, but is no longer updated.

During the migration, we made some minor adjustments to some Circulars to adapt them to the structured format of the new database:

There were two instances where the old archive added a letter suffix to a Circular ID to distinguish multiple Circulars that were initially assigned the same ID. In the new archive, we have replaced these with half-integer IDs. GCN 18448a became GCN 18448.5 and GCN 18453a became GCN 18453.5.
Some Circulars listed both a "date" and a "revised submission date". Where applicable, the date presented in the new archive is the revised submission date.
The very earliest Circulars (before GCN 31) did not record a subject, submission date, or submitter email address. Where these fields were missing, we set the subject to Untitled, the date to January 1, 1970 (the start of the UNIX epoch), and the submitter email address to circulars@gcn.nasa.gov.
Some Circulars submitted by Scott Barthelmy did not display an email address. In these cases, we have rendered the submitter as Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>.
Some Circulars have editorial remarks indicated by the text [GCN OP NOTE ...]. In most cases, this text was at the bottom of the Circular below the body text, but in a few cases it was at the top, before the headers. We have moved all [GCN OP NOTE ...] remarks to the bottom.
Some Circulars that were submitted by mistake and removed from the archive still had entries in the old archive that were hyperlinks to URLs of the format https://gcn.gsfc.nasa.gov/gcn3/mistakeN.gcn3 where N is an integer. These Circulars are removed entirely from the new archive.