GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"- EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
- EP260131a: NOT early detection of the counterpart in "rapid response mode"
- GRB 260131B: MAXI/GSC detection
- GRB 260131A: Fermi GBM Final Real-time Localization
- EP260131a: COLIBRÍ optical observations of the counterpart
- EP260131a: Las Cumbres detection of an optical counterpart
- GRB 260127B: AstroSat CZTI detection
- GRB 260130A: Fermi GBM Detection
- EP260131a: Einstein Probe detection of an X-ray transient
- GRB 260127B: Fermi GBM Detection
- EP260128a / GRB 260128A: COLIBRÍ optical upper limit
- Fermi GRB 260130A: Global MASTER-Net observations report
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- GRB 260130A: Fermi GBM Final Real-time Localization
- Fermi GRB 260129A: Global MASTER-Net observations report
- GRB 260128B: LCO optical upper limits
- GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- EP260128a: J band upper limit by SYSU 80cm infrared telescope
- IPN triangulation of GRB 260121A
- GRB 260127A: Swift-BAT refined analysis
- GRB 260129B: Fermi GBM Final Localization
- GRB 260128B: SVOM detection of a burst through offline search
- GRB 260129A: Fermi GBM Final Localization
- IPN triangulation of GRB 260127B (short)
- GRB 260127B: Swift-XRT observations
- GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
- GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
- EP260128a: NOT optical counterpart candidate
- EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260128a: Liverpool Telescope optical observations and possible counterpart
- EP260128a: LCO optical upper limits
- EP260126a: SVOM/VT optical upperlimit
- EP260128a: Global MASTER-Net observations report
- EP260128a: Einstein Probe detection of an X-ray transient
- Fermi GRB 260127A: Global MASTER-Net observations report
- IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
- GRB 260127A: Fermi GBM Observation
- IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260127A: COLIBRÍ optical observations
- GRB 260127A: NOT optical observations
- GRB 260127B: Swift ToO observations
- EP260126a: Seimei/TriCCS optical upper limit
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: Swift-XRT refined Analysis
- GRB 260127B: GOTO candidate optical counterpart
- GRB 260127A: SVOM/C-GFT optical observations
- The EP-WXT trigger 01709253145 is likely a flaring star
- GRB 260127A: Enhanced Swift-XRT position
- Fermi GRB 260127B: Global MASTER-Net observations report
- GRB 260127B: Fermi GBM Final Real-time Localization
- GRB 260127A: Prompt enhanced Swift-XRT position
- Swift GRB 260127A: Global MASTER-Net observations report
- GRB 260127A: LCO optical afterglow discovery
- GRB 260127A: Swift detection of a burst
- GRB 260127A: Fermi GBM Final Real-time Localization
- GRB 260125A: Swift-XRT observations
- EP260126a: EP-FXT follow-up observation
- EP260126a: Optical upper limit with Kinder observations
- EP260126a: Liverpool Telescope optical upper limits
- EP260126a: Further NOT optical upper limits
- EP260126a: COLIBRÍ optical upper limits
- EP260126a: NOT optical observations
- EP260126a: Einstein Probe detection of a fast X-ray transient
- Fermi-LAT Gamma-ray Observations of IceCube-260125A
- GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
- Konus-Wind detection of GRB 260120B
- GRB 251222A: SVOM/ECLAIRs refined analysis
- GRB 260125A: Swift ToO observations
- GRB 260125A: GOTO candidate optical counterpart
- Fermi GRB 260125B: Global MASTER-Net observations report
- IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260125B: Fermi GBM Final Real-time Localization
- GRB 260125A: Fermi GBM Final Real-time Localization
- GRB 260114A: SVOM/VT optical upper limits
- GRB 260120A: AstroSat CZTI detection
- GRB 260122B: Swift-BAT refined analysis
- GRB 260120B: SVOM/GRM observation
- GRB 260120A: GECAM-B observation
- GRB 260120B: AstroSat CZTI detection
- GRB 260114A: Insight-HXMT/HE detection
- GRB 260122B: Swift detection of a burst
- Swift GRB260122.97: Global MASTER-Net observations report
- EP260119a: Assy AZT-20 optical observations
- EP260119a: Mondy and SAO RAS optical upper limits
- GRB 260122A: Fermi GBM Final Real-time Localization
- IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
- EP260119a: Xinglong optical upper limit
- The EP-WXT trigger 01709251871 is likely a flaring star
- Fermi GRB 260120C: Global MASTER-Net observations report
- GRB 260120B: Swift-BAT refined analysis
- GRB 260120B: Swift-XRT refined Analysis
- EP260116a: COLIBRÍ further observations
- GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
- GRB 260120B: Fermi GBM Observation
- EP260105a: GTC/HiPERCAM optical observations
- GRB 260120B: Swift/UVOT Detection
- GRB 260120B: COLIBRÍ optical upper limits
- SVOM GRB260121.06: Global MASTER-Net observations report
- GRB 260120B: Enhanced Swift-XRT position
- GRB 260120B: SVOM/C-GFT optical counterpart detection