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"- Swift GRB191105.01: Global MASTER-Net OT detection
- GRB 191101A: Swift-BAT refined analysis
- Fermi GBM GRB 191104C (trigger 594592184 / 191104854) is not a GRB
- GRB 191104C: Fermi GBM Final Real-time Localization
- GRB 191101A: Swift/UVOT Upper Limits
- Fermi GBM GRBs 191104 A, B, C and triggers 594534420/191104185 and 594563923/191104527 are not GRBs
- SGR 1935+2154: Swift-BAT refined analysis
- Fermi trigger No 594563923: Global MASTER-Net observations report
- GRB 191104B/GRB 191104C are SGR 1935+2154
- Fermi trigger No 594557071: Global MASTER-Net observations report
- GRB 191104C: BALROG localization (Fermi Trigger 594557071 / GRB 191104448)
- GRB 191104C: Fermi GBM Final Real-time Localization
- Fermi trigger No 594551878: Global MASTER-Net observations report
- Fermi trigger No 594528816: Global MASTER-Net observations report
- GRB 191104B: Fermi GBM Final Real-time Localization
- Trigger 933083: Swift detection of SGR 1935+2154
- Fermi GBM triggers 594523229/191104056 and 594528816/191104120 are not GRBs
- GRB 191104A: Fermi GBM Final Real-time Localization
- GRB 191031D: Zwicky Transient Facility Follow-Up of a Swift Short GRB (Trigger 594249816/191031891)
- Konus-Wind observation of GRB 191031D: correction to GCN 26126
- GRB 191031E: Insight-HXMT/HE detection
- GRB 191031D: Gemini optical upper limit
- GRB 191031C: Insight-HXMT/HE detection
- GRB 191101A: iTelescope optical limit
- GRB 191101A: Swift-XRT refined Analysis
- Baksan Neutrino Observatory Alert 191102.06: Global MASTER-Net observations report
- GRB 191101A: VIRT Optical Upper Limits
- Fermi trigger No 594336535: Global MASTER-Net observations report
- GRB 191101A: Enhanced Swift-XRT position
- Swift GRB191101.88: Global MASTER-Net observations report
- Fermi trigger No 594227699: Global MASTER-Net observations report
- GRB 191101A: Prompt enhanced Swift-XRT position
- GRB 191101B: Fermi GBM Final Real-time Localization
- GRB 191101A: Swift detection of a burst
- GRB 191031D: MMT Binospec Optical Upper Limit
- GRB 191031D: Swift-BAT refined analysis
- GRB 191031C: Swift-BAT refined analysis
- GRB 191031A: Swift-BAT refined analysis
- 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