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.
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"28082 results found.
- EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
- Fermi trigger No 804738310: Global MASTER-Net observations report
- Fermi GRB 260703A: Global MASTER-Net observations report
- GRB 260623A: Glowbug gamma-ray detection
- GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
- Fermi trigger No 804552016: Global MASTER-Net observations report
- GRB 260701A: Fermi GBM Final Real-time Localization
- Fermi-LAT Gamma-ray Observations of IceCube-260622A
- EP260628a: EP-FXT follow-up observation
- Fermi GRB 260628A: Global MASTER-Net observations report
- EP260628a: EP-WXT detection of a fast X-ray transient
- EP260626a: further Liverpool Telescope optical upper limits
- EP260626a: COLIBRÍ optical upper limit
- EP260626a: Liverpool Telescope upper limits
- EP260626a: EP-WXT detection of a fast X-ray transient
- EP260623a: TNG NIR afterglow detection
- GRB 260618A: Fermi GBM Observation
- GRB 260619A: SVOM/ECLAIRs refined analysis
- EP260623a: Liverpool Telescope optical observations
- EP260623a:refined analysis of the EP-WXT and EP-FXT observation
- EP260623a: WINTER J-band observations
- GRB 260617A: Glowbug gamma-ray detection of a short burst
- IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
- EP260623a: Optical follow-up observations with Kinder
- EP260623a: SVOM/VT optical observations
- EP260623a: TRT optical observations
- EP260623a: REM optical/NIR afterglow detection
- EP 260623a: COLIBRÍ optical observations
- GRB 260616B/EP260616a: Insight-HXMT/HE detection
- EP260623a: Las Cumbres discovery of the optical counterpart
- EP260623a: Einstein Probe detection of an X-ray transient
- GRB 260614B: EP-FXT follow-up observation
- GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
- EP260618a: Liverpool Telescope optical observations
- GRB 260618B: LCO optical observations
- EP260618a: JinShan optical observations
- GRB 260616B/EP260616a: SVOM/GRM detection of a burst
- GRB 260618B: Fermi GBM Observation
- IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260619A: TRT optical counterpart confirmation
- GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
- Fermi-LAT Gamma-ray Observations of IceCube-260610A
- GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
- GRB 260616B: AstroSat CZTI detection
- GRB 260616A: AstroSat CZTI detection
- GRB 260616A: SVOM/GRM observation
- EP260618a: OHP/T193 optical observations
- GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
- GRB 260619A: Kilonova-Catcher optical upper limit
- EP260618a: LCO optical counterpart confirmation
- EP260618a: COLIBRÍ optical counterpart candidate
- GRB 260616A: NuSTAR detection of prompt emission
- GRB 260614B: NuSTAR detection of prompt emission
- GRB 260619A: SVOM possible detection of a faint burst
- IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
- EP260618a: EP-WXT detection of an X-ray transient
- GRB 260610B: AbAO optical observations
- GRB 260506B: cubesat Avion detection
- GRB 260617A: Fermi GBM Detection
- GRB 260616A: Fermi GBM Observation
- EP260616a/GRB260616B: COLIBRÍ optical upper limit
- GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
- GRB 260429A: cubesat Avion detection
- GRB260616C: MAXI/GSC detection
- GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
- EP260616a: EP-WXT detection of a fast X-ray transient
- GRB 260616B: Fermi GBM Detection
- GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
- GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
- GRB 260610B: Terskol optical observations
- GRB 260610B: SVOM/GRM observation
- GRB 260614B: Fermi GBM Observation
- GRB 260614B: SVOM/VT optical candidate from VHF data
- GRB 260614B: SVOM detection of a burst
- GRB 260611B: SVOM/GRM detection
- The EP-WXT trigger 01709269488 is likely a flaring star
- GRB 260610B: further Liverpool Telescope optical observations
- GRB 260610B: Fermi GBM Observation
- GRB 260610B / AT2026owq: GRANDMA optical observations
- GRB 260610B / AT2026owq: further SAO RAS optical observations
- EP260605a: COLIBRÍ optical upper limits
- GRB 260610b: Liverpool Telescope optical observations
- EP260610b: Liverpool Telescope optical upper limits
- The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
- GRB 260610B / AT2026owq: SAO RAS optical observations
- EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260610B / AT 2026owq: COLIBRÍ optical observations
- GRB 260610B / AT2026owq: Early ATLAS observations
- GRB 260610B: TRT optical observation
- EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260610b: COLIBRÍ optical observations
- GRB 260610B: DDOTI optical observations
- EP260610b: MAO/AZT-22 optical observations
- EP260610b: NOT optical observation
- EP260610b: SVOM/VT optical confirmation with blue color
- GRB 260515A: SOAR optical observations
- EP260610a: SVOM/VT optical upper limits
- EP260610b: Einstein Probe detection of an X-ray transient
- EP260610a: COLIBRÍ optical upper limits
- EP260610a: Einstein Probe detection of a fast X-ray transient