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 191031C: Swift-XRT refined Analysis
- GRB 191031D: AstroSat CZTI detection
- GRB 191031D: Swift/UVOT Upper Limits
- GRB 191031C: Swift/UVOT Detection
- Konus-Wind observation of GRB 191031D
- GRB 191031D: MITSuME Akeno optical upper limits
- GRB 191031D: Swift-XRT refined Analysis
- GRB 191031D: AGILE/MCAL observations
- GRB 191031D: COATLI Optical Observations
- GRB 191031D: RATIR Optical and NIR Observations
- GRB 191031D: VLA 9.8 GHz upper limit
- GRB 191031C: Fermi GBM detection
- GRB 191031D: Fermi GBM detection
- GRB 191031D: Enhanced Swift-XRT position
- GRB 191031A: Fermi GBM detection
- GRB 191031C: Enhanced Swift-XRT position
- Correction in name: GRB 191031D (not GRB 191031C)
- Swift GRB191031.89: Global MASTER-Net observations report
- GRB 191031D: Swift detection of a short hard burst
- GRB 191031C: Fermi GBM Final Real-time Localization
- GRB 191029A: Swift-BAT refined analysis
- GRB 191031C: Prompt enhanced Swift-XRT position
- GRB 191031C: Swift detection of a burst
- GRB 191031C: Fermi GBM Final Real-time Localization
- GRB 191025B: AstroSat CZTI detection
- Fermi trigger No 594175000: Global MASTER-Net observations report
- GRB 191031B: Fermi GBM Final Real-time Localization
- GRB 191031A: COATLI Optical Observations
- GRB 191031A: Fermi GBM Final Real-time Localization
- GRB 191031A: Swift detection of a burst
- Konus-Wind observation of GRB 191027A
- GRB 191029A: CORRECTED Swift-XRT refined analysis
- GRB 191019A: Zadko Telescope optical observations
- GRB 191029A: Swift/UVOT Upper Limits
- Correction to GCN 26079 regarding GRB 191027A
- GRB 191029A: Enhanced Swift-XRT position
- GRB 191029A: Swift-XRT refined Analysis
- GRB 191028B: MASTER optical observation
- GRB 191029A: BOOTES-4/MET optical limit
- GRB 191029A: iTelescope optical upper limits
- GRB 191029A: Swift-XRT observations
- Konus-Wind observation of GRB 191025B
- GRB 191029A: Swift detection of a burst
- IPN triangulation of GRB 191027A
- IPN triangulation of GRB 191025B (short)
- GRB 191028B: BALROG localization (Fermi Trigger 593964489 / GRB 191028589)
- GRB 191028B: Fermi GBM Final Real-time Localization
- Fermi GBM trigger 593931926/191028212 is not a GRB
- GRB 191028A: Fermi GBM Final Real-time Localization
- GRB 191025B: Insight-HXMT/HE detection
- Swift/BAT Trigger 931384 is not a GRB ( 191025A )
- GRB 191027A: BALROG localization (Fermi Trigger 593882352 / GRB 191027638)
- GRB 191027A: Fermi GBM Final Real-time Localization
- GRB 191026B: AstroSat CZTI detection
- GRB 191026A: Fermi GBM Final Real-time Localization
- Swift Trigger 931484 is not a GRB
- GRB 191023A: MASTER optical observation
- Possible GRB 191025A: FRAM-Auger optical limit
- Swift Trigger 931384: possible GRB 191025A
- GRB 191024A: Swift-BAT refined analysis
- GRB 191024A: Swift/UVOT Upper Limits
- GRB 191024A: Afterglow Upper Limits with LCO
- GRB 191024A: Swift-XRT refined Analysis
- GRB 191024A: VLT/X-shooter optical observations
- GRB 191024A: GROND early upper limits
- GRB191024A: MASTER optical observation
- GRB 191024A: Enhanced Swift-XRT position
- GRB 191024A: Swift detection of a burst
- GRB 191019A: NOT optical afterglow and host association confirmation
- GRB 191023A: BALROG localization (Fermi Trigger 593536021 / GRB 191023630)
- GRB 191023A: Fermi GBM Final Real-time Localization
- GRB 191019A: Nanshan-0.6m optical observations
- GRB 191019B: AstroSat CZTI detection
- GRB 191022B: Fermi GBM Final Real-time Localization
- GRB 191022A: BALROG localization (Fermi Trigger 593419810 / GRB 191022285)
- GRB 191022A: Fermi GBM Final Real-time Localization
- Swift GRB191020.89: Global MASTER-Net OT detection
- GRB 191019A: Swift/UVOT Detection
- HAWC-191019A: Retraction of burst alert
- MASTER correction to GCN Circ. 26044 and 26047
- GCN Circ. 26044 and 26047 are mistakenly submission GRB reports
- HAWC-191019A: No Neutrino Counterpart detected with ANTARES
- GRB 191019A: Swift-XRT updated analysis
- Swift GRB191020.81: Global MASTER-Net OT detection
- GRB 191019A: Swift-BAT refined analysis
- GRB 191019A: Swift-XRT refined Analysis
- Swift GRB191019.67: Global MASTER-Net observations report
- GRB 191019A: Enhanced Swift-XRT position
- GRB 191019A: GROND observations
- GRB 191019A: NOT optical spectroscopy of candidate counterpart
- GRB 191019B: Fermi GBM Final Real-time Localization
- GRB 191019A: NOT optical observations
- Fermi trigger No 593176520: Global MASTER-Net observations report
- Alert from the HAWC Burst Monitor HAWC-191019A
- GRB 191019A: TSHAO optical observations, probable afterglow and host galaxy
- FACT follow-up of ANTARES-Fermi 191011A
- GRB 191019A: Swift-XRT observations
- Swift GRB191019.63: Global MASTER-Net observations report
- GRB 191019A: MASTER optical observation
- GRB 191019A: Swift detection of a burst