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"16109 results found.
- GRB 260708A: GRANDMA Optical Observations
- Fermi-LAT Gamma-ray Observations of IceCube-260708A
- GRB 260708A: LCO optical observations
- GRB 260709A: SVOM/GRM detection
- EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
- GRB 260708A: Glowbug gamma-ray detection
- GRB 260706A : GRANDMA Upper limits
- GRB 260708A: Kilonova-Catcher optical afterglow detection
- Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
- GRB 260705B: SVOM/GRM observation
- GRB 260706A: SVOM/VT optical upper limits
- EP260707a (by EP-FXT): NOT optical upper limit
- EP260707a is not a real source
- EP260707a: LCOGT Optical Upper Limit
- EP260707a: TRT optical upper limit
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- GRB 260706A: REM optical/NIR observations
- IceCube-260704A: No candidates from the Zwicky Transient Facility
- GRB 260706A: LCO optical upper limit
- GRB 260706A: SVOM detection of a burst
- IceCube260704A: OHP/T193 optical observations
- GRB 260705A: LCO optical upper limits
- GRB 260704A: NOT optical upper limits
- GRB 260705A: SVOM detection of a burst
- GRB 260629A: SVOM/GRM observation of a short burst
- GRB 260610B: VLA detection
- GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
- EP260626a: further Liverpool Telescope optical upper limits
- EP260626a: EP-FXT follow-up observation
- EP260626a: COLIBRÍ optical upper limit
- EP260623a: FTW optical and NIR observations
- EP260623a: Liverpool Telescope optical observations
- EP260623a:refined analysis of the EP-WXT and EP-FXT observation
- 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
- 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