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"27770 results found.
- GRB260708B: MAXI/GSC detection
- GRB 260708A: Fermi-LAT detection
- GRB 260708A: Fermi-GBM detection
- GRB 260706A: Further EP-FXT follow-up observation
- GRB 260706A: SVOM/VT optical upper limits
- EP260707a: Einstein Probe detection of an X-ray transient
- Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- GRB 260705C: Glowbug gamma-ray detection of a short burst
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- IceCube-260704A: No candidates from the Zwicky Transient Facility
- GRB 260707A: Fermi GBM Final Real-time Localization
- GRB 260706A: SVOM detection of a burst
- GRB 260706A: Fermi GBM Final Real-time Localization
- GRB 260705C: Fermi GBM Final Localization
- GRB 260705B: Fermi GBM Final Real-time Localization
- Fermi GBM Sub-Threshold Detection of GRB 260705A
- GRB 260705A: SVOM detection of a burst
- IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260629A: AstroSat CZTI detection
- EP260703a: EP-FXT follow-up observation
- GRB 260704A: SVOM detection of a possible GRB
- GRB 260703B: Fermi GBM Final Localization
- EP260703a: EP-WXT detection of a fast X-ray transient
- EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
- GRB 260703A: Fermi GBM Final Localization
- GRB 260610B: VLA detection
- GRB 260623A: Glowbug gamma-ray detection
- GRB 260701A: Fermi GBM Final Real-time Localization
- EP260628a: EP-FXT follow-up observation
- GRB 260629A: Fermi GBM Final Real-time Localization
- EP260628a: EP-WXT detection of a fast X-ray transient
- GRB 260628A: Fermi GBM Final Real-time Localization
- EP260626a: EP-FXT follow-up observation
- EP260626a: Liverpool Telescope upper limits
- EP260626a: EP-WXT detection of a fast X-ray transient
- Konus-Wind detection of GRB 260623B / EP260623a
- EP260623a: TNG NIR afterglow detection
- MASS-Cube (GRID 2.0) detection of GRB 260616B
- Konus-Wind detection of GRB 260618B
- GRB 260624A: Fermi GBM Final Real-time Localization
- GRB 260617A: Glowbug gamma-ray detection of a short burst
- IPN triangulation of GRB 260605A
- EP260623a: Optical follow-up observations with Kinder
- EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
- GRB 260623A: Fermi GBM Final Real-time Localization
- EP260623a: REM optical/NIR afterglow detection
- EP 260623a: COLIBRÍ optical observations
- GRB 260616B/EP260616a: Insight-HXMT/HE detection
- EP260623a: Einstein Probe detection of an X-ray transient
- IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
- GRB 260616B/EP260616a: SVOM/GRM detection of a burst
- GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
- GRB 260604B: 239Alferov CubeSat detection
- GRB 260604A: 239Alferov CubeSat detection
- GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
- Konus-Wind detection of GRB 260617A
- GRB 260616B: AstroSat CZTI detection
- GRB 260616A: AstroSat CZTI detection
- GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
- EP260618a: EP-FXT follow-up observation
- GRB 260617A: CALET Gamma-Ray Burst Monitor detection
- GRB 260616A: NuSTAR detection of prompt emission
- GRB 260614B: NuSTAR detection of prompt emission
- GRB 260619A: SVOM possible detection of a faint burst
- GRB 260618B: Fermi-LAT detection
- IPN triangulation of GRB 260617A (short)
- GRB 260610B/AT 2026owq: FTW optical and NIR observations
- GRB 260616A: Insight-HXMT detection
- GRB 260618B: Fermi GBM Final Real-time Localization
- EP260618a: EP-WXT detection of an X-ray transient
- EP260616a/GRB 260616B: EP-FXT follow-up observation
- GRB 260506B: cubesat Avion detection
- GRB 260618A: Fermi GBM Final Real-time Localization
- GRB 260617A: Fermi GBM Detection
- GRB 260617A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 260616B/EP260616a
- Konus-Wind detection of GRB 260616A
- GRB 260616B: CALET Gamma-Ray Burst Monitor detection
- GRB 260429A: cubesat Avion detection
- GRB260616C: MAXI/GSC detection
- GRB 260616A: Fermi-LAT detection
- GRB 260614A: AstroSat CZTI detection
- EP260616a: EP-WXT detection of a fast X-ray transient
- GRB 260616B: Fermi GBM Detection
- GRB 260616A: Fermi GBM Final Real-time Localization
- GRB 260610B: ALMA detection
- GRB 260614B: SVOM detection of a burst
- GRB 260614B: Fermi GBM Final Real-time Localization
- GRB 260611B: SVOM/GRM detection
- GRB 260614A: Fermi GBM Final Localization
- GRB 260603C: AstroSat CZTI detection
- EP260610b: Liverpool Telescope optical upper limits
- GRB 260611B: CALET Gamma-Ray Burst Monitor detection
- GRB 260611B: Fermi GBM Final Real-time Localization
- GRB 260610B / AT2026owq: Early ATLAS observations
- GRB 260611A: Fermi GBM Final Real-time Localization
- GRB 260610B: Fermi GBM Final Localization
- IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event