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"15985 results found.
- EP260623a: REM optical/NIR afterglow detection
- EP 260623a: COLIBRÍ optical observations
- EP260623a: OSIRIS+/GTC redshift z = 0.703
- EP260623a: Las Cumbres discovery of the optical counterpart
- GRB 260614B: EP-FXT follow-up observation
- EP260618a: Liverpool Telescope optical observations
- GRB 260619A: NOT optical observations
- GRB 260618B: LCO optical observations
- EP260618a: JinShan optical observations
- GRB 260616B/EP260616a: SVOM/GRM detection of a burst
- GRB 260619A: TRT optical counterpart confirmation
- 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
- GRB 260618B: SVOM/VT optical candidate
- GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
- GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
- 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: EP-FXT follow-up observation
- EP260618a: LCO optical counterpart confirmation
- EP260618a: COLIBRÍ optical counterpart candidate
- GRB 260610B/AT 2026owq: FTW optical and NIR observations
- GRB 260610B: AbAO optical observations
- EP260616a/GRB 260616B: EP-FXT follow-up observation
- EP260616a/GRB260616B: COLIBRÍ optical upper limit
- GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
- GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
- GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
- GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
- GRB 260610B: Terskol optical observations
- GRB 260610B: SVOM/GRM observation
- GRB 260614B: SVOM/VT optical afterglow confirmation
- GRB 260610B: ALMA detection
- GRB 260614B: SVOM/VT optical candidate from VHF data
- GRB 260611B: SVOM/GRM detection
- 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
- 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
- EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
- EP260610b: GTC likely spectroscopic redshift z = 1.10
- GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
- 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
- GRB 260610B: GOTO optical counterpart candidate
- EP260610b: NOT optical observation
- EP260610b: SVOM/VT optical confirmation with blue color
- GRB 260515A: SOAR optical observations
- EP260610b: Gemini North optical counterpart candidate
- EP260610a: SVOM/VT optical upper limits
- EP260610a: COLIBRÍ optical upper limits
- 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/C-GFT upper limit
- GRB 260608A: SVOM detection of a burst
- GRB 260607A: TRT optical observations
- GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
- GRB 260604A: SVOM/GRM detection
- GRB 260604C: Mondy optical observations: evidence of a possible brightening
- GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
- GRB 260604C: 6 GHz VLA observations
- GRB 260604C: SAO RAS optical observations
- GRB 260604C: GRANDMA observations
- GRB 260604B: SVOM/GRM detection
- EP260603a: COLIBRÍ optical upper limit
- GRB 260604C: LCO optical upper limit
- GRB 260604C: Liverpool Telescope optical detection
- EP260602d: EP-FXT follow-up observation
- GRB 260604C: GOTO detections of the optical afterglow
- GRB 260604C: Correction to GCN 44828
- GRB 260604C: Kilonova-Catcher optical afterglow detection
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260604C: Jinshan optical observations
- 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
- GRB 260604C: SVOM detection of a long burst
- GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
- GRB 260603A: NOT optical observations
- GRB 260603A: Simeiz Zeiss-1000 optical upper limit
- EP260602a: EP-FXT follow-up observation
- EP260602d: Optical Upper limits with kinder observations
- EP260602b: Liverpool Telescope observations
- EP260602a: Liverpool Telescope optical upper limits