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Circulars Archive

Upon successful submission and distribution, a GCN Circulars 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

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 The old GCN Classic Circulars archive page is preserved, but is no longer updated.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
  • 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 <>.
  • 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 where N is an integer. These Circulars are removed entirely from the new archive.
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