GCN Circulars
GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search
To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.
Advanced Search Examples (click to copy):
subject:"Swift"body:"GRB"submitter:"Judith Racusin"- GRB 060418, SMARTS optical/IR afterglow observations
- GRB060418: Magellan/MIKE Spectroscopic Redshift
- GRB060418 : LT optical afterglow observation
- GRB 060418: REM candidate afterglow
- GRB 060418: Swift detection of a burst with bright x-ray and optical afterglow
- SGR 1900+14: Refined analysis of the Swift-BAT outburst
- GRB060413: Swift/UVOT upper limits
- GRB 060413: REM NIR Observations
- SGR 1900+14: Swift detection of an outburst
- GRB 060413: Refined analysis of the Swift-BAT burst
- GRB 060413: Watcher UBVR observations
- GRB 060413: XRT refined analysis
- GRB 060413: No Optical Afterglow in Swift/UVOT TDRSS Data
- GRB 060413: Swift detection of a burst
- GRB060403: optical observations
- GRB 060403 Optical observations
- GRB 060403: MITSuME optical observation
- GRB060403: Optical Limit
- GRB060403: XRT refined analysis
- GRB 060403: Swift/UVOT upper limits
- HETE Triggers H4043 and H4044 Not Due to New Cosmic Source
- SGR 1900+14: BAT observations
- GRB 060403: Refined analysis of the Swift-BAT burst
- GRB060403: Swift XRT refined position
- Konus-Wind observation of the recent SGR 1900+14 activity. Will
- GRB 060403: Swift detection of a burst
- HETE trigger H4044: RTT150 optical observations
- GRB060331: Swift/UVOT upper limits
- H4044, a Repeat Outburst From The Source of H4043 (="GRB060331")
- Swift XRT observations of the HETE transient H4043
- HETE Trigger 4043: ROTSE-III Optical Limits
- Correction to Circular 4938, =H4043, an unusual high energy transient observed by HETE
- H4043, an unusual high-energy transient observed by HETE
- GRB 060322: LNA optical limit
- SGR 1900+14: bright burst detected by Konus-Wind on March 28
- INTEGRAL and XMM ToO observations of SGR1900+14
- SGR 1900+14: Swift-BAT detection of a cluster of outbursts
- SGR 1900+14: Swift-BAT detection of a bright outburst
- GRB 060218SN 2006aj: optical observations at Rozhen Observatory
- GRB 060323 : WIDGET simultaneous optical observations
- GRB 060323: Early optical observation at Xinglong
- GRB060218, optical observations
- GRB 060322: Confirmation of Swift XRT afterglow
- GRB 060211A: optical observation
- GRB060323: optical limit
- GRB060211B: optical observation
- SGR 1900+14: CORRECTION to GCN 4923
- SGR 1900+14: Refined Swift-BAT analysis of the renewed activity
- SGR 1900+14: Swift detection of renewed activity
- GRB060323: NOT optical observations
- GRB 060322: IAC80 optical observations
- GRB 060322: Swift XRT afterglow candidate
- GRB060323: P60 Observations
- GRB 060323: Swift/UVOT Observations
- GRB 060323: optical afterglow confirmed
- GRB060323: NOT observations
- GRB 060323: Optical Observations
- GRB 060323: Tautenburg OT candidate retraction
- GRB 060323: Refined analysis of the Swift-BAT burst
- GRB 060323: optical observations at TNG
- GRB 060323: Swift XRT refined analysis
- GRB 060323: BVRI observations at Tautenburg, aftreglow candidate
- GRB 060323: Swift/XRT position
- GRB 060322: Refined analysis of the Swift-BAT burst
- GRB060323, optical observation
- GRB060323 - SDSS Pre-Burst Observations
- GRB 060323: Swift detection of a burst with a possible optical afterglow
- GRB 060322: Swift-BAT detection of a 200-sec burst
- GRB060219: optical observation
- GRB060206: optical observation
- GRB060218/SN2006aj: optical observations
- GRB 060218/SN 2006aj, LNA optical observation
- GRB060218: Refined photometric calibration of comparison stars
- GRB 060319: WHT K-band candidate afterglow
- GRB 060319: IAC-80 optical observations
- GRB060319: Swift XRT refined analysis
- GRB060319: Swift/UVOT upper limits
- GRB 060319: Re-analysis of TNG data
- GRB060319: MASTER limit
- GRB 060319: Swift-BAT refined analysis
- GRB 060319 optical observations at TNG
- GRB060319 : Liverpool Telescope optical limit
- GRB060319: MASTER optical observation
- GRB060319 - SDSS Pre-burst Observations
- GRB060319: Swift/XRT position
- GRB 060319: Swift detection of a burst
- GRB060313: Radio Observations
- GRB 060313: early afterglow NIR upper limits with REM
- IBAS Alert n. 3221: not a GRB
- Konus-Wind observation of GRB 060313
- GRB060313: SSO 40inch Observations
- GRB 060313: Further analysis of the Swift-BAT bright short hard burst
- GRB 060313: PROMPT Observations
- GRB 060313: Swift/UVOT Observations
- GRB060313:Gemini South Observations
- GRB 060313: Swift-XRT team refined analysis
- GRB060313: optical observations of the afterglow candidate
- GRB 060313: Refined analysis of the Swift-BAT bright short hard burst
- GRB 060313, SMARTS optical counterpart?
- GRB 060313: Possible optical counterpart