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"20951 results found.
- Fermi trigger No 804552016: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260622A
- Fermi GRB 260628A: Global MASTER-Net observations report
- EP260628a: EP-WXT detection of a fast X-ray transient
- EP260626a: EP-WXT detection of a fast X-ray transient
- EP260623a: FTW optical and NIR observations
- GRB 260619A: SVOM/ECLAIRs refined analysis
- EP260623a: Liverpool Telescope optical observations
- EP260623a: WINTER J-band observations
- EP260623a: Optical follow-up observations with Kinder
- EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
- EP260623a: SVOM/VT optical observations
- EP260623a: TRT optical observations
- EP260623a: REM optical/NIR afterglow detection
- EP 260623a: COLIBRÍ optical observations
- GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
- EP260618a: Liverpool Telescope optical observations
- GRB 260619A: NOT optical observations
- GRB 260618B: LCO optical observations
- EP260618a: JinShan optical observations
- GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
- GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
- GRB 260619A: SVOM/VT optical counterpart confirmation
- Fermi-LAT Gamma-ray Observations of IceCube-260610A
- GRB 260618B: SVOM/VT optical candidate
- GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
- EP260618a: OHP/T193 optical observations
- GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
- GRB 260619A: Kilonova-Catcher optical upper limit
- EP260618a: EP-FXT follow-up observation
- EP260618a: COLIBRÍ optical counterpart candidate
- GRB 260610B/AT 2026owq: FTW optical and NIR observations
- EP260618a: EP-WXT detection of an X-ray transient
- GRB 260610B: AbAO optical observations
- EP260616a/GRB 260616B: EP-FXT follow-up observation
- GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
- GRB260616C: MAXI/GSC detection
- GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
- GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
- EP260616a: EP-WXT detection of a fast X-ray transient
- GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
- GRB 260604C: GRANDMA late observations with CFHT/MegaCam
- GRB 260614B: SVOM/ECLAIRs refined analysis
- GRB 260610B: Terskol optical observations
- GRB 260614B: SVOM/VT optical afterglow confirmation
- GRB 260610B: ALMA detection
- GRB 260610B: further Liverpool Telescope optical observations
- 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
- IceCube-260610A: No candidates from the Zwicky Transient Facility
- IceCube-260610A: EP-FXT follow-up observation
- The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
- GRB 260610B / AT2026owq: SVOM/VT optical observations
- GRB 260610B / AT2026owq: OASDG optical observations
- GRB 260610B: IAC-80 Optical observations
- GRB 260610B / AT2026owq: SAO RAS optical observations
- EP260610b: GTC likely spectroscopic redshift z = 1.10
- 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
- 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
- GRB 260610B: GOTO optical counterpart candidate
- EP260610b: SVOM/VT optical confirmation with blue color
- GRB 260515A: SOAR optical observations
- EP260610b: Gemini North optical counterpart candidate
- GRB 260604C: SVOM/ECLAIRs refined analysis
- GRB 260608A: SVOM/ECLAIRs refined analysis
- GRB 260604C: further SAO RAS optical observations
- GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
- GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
- GRB 260604C: SVOM/C-GFT upper limit
- GRB 260607A: TRT optical observations
- GRB 260604C: GRANDMA further observations
- GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
- GRB 260604C: Mondy optical observations: evidence of a possible brightening
- GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
- GRB 260604C: OPD1.6m - GRANDMA observations - detection
- GRB 260604C: 6 GHz VLA observations
- GRB 260604C: SAO RAS optical observations
- GRB 260604C: GRANDMA observations
- GRB260603A: SVOM/ECLAIRs refined analysis
- GRB 260604C: Liverpool Telescope optical detection
- EP260602d: EP-FXT follow-up observation
- GRB 260527A/EP260527a: 6 GHz VLA observations
- GRB 260604C: GOTO detections of the optical afterglow
- GRB 260604C: Kilonova-Catcher optical afterglow detection
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260604C: Jinshan optical observations
- EP260602d: J-band upper limit with WINTER
- EP260602b: J-band upper limit with WINTER
- GRB 260604C: LAST detection of optical counterpart candidate
- GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
- Fermi GRB 260604C: Global MASTER-Net observations report
- Fermi GRB 260604C: Global MASTER-Net observations report