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 181028A: Fermi-LAT detection
- GRB 181027A: Fermi GBM detection
- GRB 181027A: Swift-BAT refined analysis
- GRB 181027A: Swift detection of a burst
- IceCube-181023A: HAWC follow-up
- IceCube-181023A: MASTER Net optical alert and follow up observations
- Search for counterparts to IceCube-181023A with IceCube
- GRB 180728B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 554505003)
- Fermi-LAT Gamma-ray Observations of IceCube-181023A
- GRB 181023A: Swift-BAT refined analysis
- GRB 181023A: Swift/UVOT Upper Limits
- IceCube-181023A - IceCube observation of a high-energy neutrino candidate event
- GRB 181022A: Swift-XRT refined Analysis
- GRB 181023A: Swift-XRT refined Analysis
- GRB 181022A: MITSuME Akeno optical upper limits
- GRB 181022A: GROND upper limits
- GRB 181022A: LCO Sutherland observations
- GRB 181023A: Enhanced Swift-XRT position
- GRB 181023A: KAIT Optical Upper Limit
- GRB 181022A: Swift/UVOT Upper Limits
- GRB 181023A: Swift detection of a burst
- GRB 181022A: Swift-BAT refined analysis
- GRB 181022A: Swift detection of a burst
- Konus-Wind observation of GRB 181020A
- GRB 181020A: REM detection
- Baksan Neutrino BNO 181021: Global MASTER-net Optical Follow-up Observations
- GRB 181020A: Swift/UVOT Detection
- GRB 181020A: Global MASTER Net OT observations
- GRB 181020A: LCO Cerro Tololo observations
- GRB 181020A: Swift-BAT refined analysis
- GRB 181020A: VLT/X-shooter spectroscopy and redshift
- GRB 181018A: Insight-HXMT/HE detection
- GRB 181017A: Insight-HXMT/HE detection
- GRB 181020A: Swift-XRT refined Analysis
- GRB 181020A: Fermi GBM detection
- GRB 181020A: Enhanced Swift-XRT position
- GRB 181020A: Fermi-LAT detection
- GRB 181020A: Swift detection of a burst with an optical counterpart
- FRB 181016: MASTER optical inspection of the Fast Radio Burst error box
- GRB 181014A: Insight-HXMT/HE detection
- Fermi GBM Observation of IceCube-181014A
- GRB 181011A: MITSuME Akeno and Okayama optical upper limits
- Trigger 867343: Swift detection of SGR1806-20
- GRB 181016A: Swift-BAT refined analysis
- GRB 181016A: Swift detection of a burst
- GRB 181013A: AbAO optical upper limit
- Search for counterparts to IceCube-181014A with IceCube
- Fermi-LAT Gamma-ray Observations of IceCube-181014A
- IceCube-181014A - IceCube observation of a high-energy neutrino candidate event
- Trigger 866993: Swift detection of SGR1806-20
- GRB 181013A: Swift/UVOT Upper Limits
- GRB 181013A: Swift-BAT refined analysis
- GRB 181013A: Swift-XRT afterglow detection
- GRB 181013A: Global MASTER Net optical observations
- GRB 181013A: Swift detection of a probable burst
- Swift Trigger 866757: is probably not a GRB
- GRB 181011A: Global MASTER Net optical inspection
- GRB 181011A: CALET Gamma-Ray Burst Monitor detection
- IPN Triangulation of GRB 181011A (long)
- GRB 181011A: MAXI/GSC detection
- GROND afterglow detection of GRB 181010A
- GRB180913A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 558557292)
- GRB 181010A: REM optical and NIR afterglow detection
- GRB 181008B: Global MASTER Net optical inspection
- GRB 181010A: Swift-BAT refined analysis
- GRB 181010A: Fermi GBM observation
- GRB 181010A: ePESSTO NTT optical observations
- IPN Triangulation of GRB 181008B (long)
- GRB 181010A: Swift/UVOT Detection
- GRB 181010A: Swift-XRT refined Analysis
- GRB 181010A: VLT/X-shooter redshift
- GRB 181008A: Insight-HXMT/HE detection
- GRB 181010A: Enhanced Swift-XRT position
- GRB 181010A: RATIR Optical and NIR Afterglow Detection
- GRB 181010A: LCO Cerro Tololo observations
- GRB 181010A: MASTER-Argentina OT detection
- GRB 181010A: Swift detection of a burst with an optical counterpart
- GRB 181002A: Mondy optical upper limit
- GRB 181003A: RATIR Optical and NIR Observations
- GRB 181003A: Swift-BAT refined analysis
- GRB 181003A: Swift-XRT afterglow detection
- GRB 180925A: Astrosat CZTI detection
- GRB 181003A: Swift/UVOT Upper Limits
- GRB 180930A: TSHAO optical upper limit
- GRB 181002A: Swift-XRT refined Analysis
- GRB 181003A: LCO Cerro Tololo observations
- GRB 181003A: MASTER optical observation
- GRB181002A: GOTO optical limits
- GRB 181002A: Swift/UVOT Upper Limits
- GRB 181003A: Swift-XRT observations
- GRB 181003A: Swift detection of a burst
- GRB 181002A: Swift-BAT refined analysis
- GRB 181002A: MASTER optical observation
- GRB 181002A: Enhanced Swift-XRT position
- Konus-Wind observation of GRB 180925A
- GRB 181002A: Swift detection of a burst
- Trigger 864882: Swift detection of Crab in its normal state
- GRB 180914B: RTT150 optical observations
- GRB 180914B: RTT150 optical observations
- GRB 180930A: Swift-BAT refined analysis