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"4223 results found.
- IceCube Alert 260825A: Global MASTER-Net observations report
- GRB 260818B: VLA radio observations
- GRB 260818B: SVOM/GRM observation
- EP260812a: AZT-22 optical upper limit
- GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
- GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
- GRB 260809A: NOT optical observations
- EP260809a: J-band upper limit with WINTER
- GRB 260808B: LCO optical observations
- Fermi GRB 260808A: Global MASTER-Net observations report
- SN 2026stf / GRB 260708A: ATLAS forced photometry
- Fermi GRB 260802B: Global MASTER-Net observations report
- GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
- EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
- EP260723a: SVOM/VT optical observation
- Fermi GRB 260718A: Global MASTER-Net observations report
- GRB 260310A / AT2026fgk: Late-time Chandra Detection
- EP260711a: EP-FXT follow-up observation
- GRB 260629A: AstroSat CZTI detection
- GRB 260703A: Fermi GBM Final Localization
- Fermi trigger No 804552016: Global MASTER-Net observations report
- GRB 260629A: Fermi GBM Final Real-time Localization
- Fermi GRB 260628A: Global MASTER-Net observations report
- EP260623a: TNG NIR afterglow detection
- EP260623a: WINTER J-band observations
- GRB 260619A: SVOM possible detection of a faint burst
- GRB 260506B: cubesat Avion detection
- GRB 260429A: cubesat Avion detection
- GRB 260610B: further Liverpool Telescope optical observations
- GRB 260610B / AT2026owq: GRANDMA optical observations
- EP260605a: COLIBRÍ optical upper limits
- EP260610b: Liverpool Telescope optical upper limits
- GRB 260610B / AT2026owq: SVOM/VT optical observations
- GRB 260604C: SVOM/C-GFT upper limit
- EP260602a: COLIBRÍ optical observations
- SVOM GRB260603.23: Global MASTER-Net observations report
- Fermi GRB 260602B: Global MASTER-Net observations report
- Fermi GRB 260602B: Global MASTER-Net observations report
- GRB 260602A: Fermi GBM Final Real-time Localization
- EP260530a/AT 2026nwl: COLIBRÍ optical observations
- AT2026nik: EP-FXT X-ray counterpart
- Fermi trigger No 801900520: Global MASTER-Net observations report
- EP260527a/GRB 260527A: further FTW optical and NIR observations
- GRB 260527A / EP260527a: VLA radio detection
- GRB 260529A: GOTO tentative optical afterglow candidate
- Fermi GRB 260529A: Global MASTER-Net observations report
- GRB 260529A: Fermi GBM Final Real-time Localization
- GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
- EP260527a: SVOM/VT optical observation
- Fermi trigger No 801580882: Global MASTER-Net observations report
- EP260526.405: COLIBRÍ optical upper limits
- EP-WXT 01709266106: NOT optical upper limits
- GRB 260515A: OHP/T193 optical observations
- SVOM GRB 260515A: Global MASTER-Net observations report
- GRB 260511B: Mephisto multi-band optical followup
- Fermi GRB 260514A: Global MASTER-Net observations report
- GRB 260511B SVOM/C-GFT optical counterpart detection
- Fermi GRB 260511A: Global MASTER-Net observations report
- GRB 260510C: MAXI/GSC detection
- EP260509a: Global MASTER-Net observations report
- SVOM GRB 260509A: MASTER-OAFA optical observation
- Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
- SVOM GRB 260504B: MASTER-OAFA optical observations
- SVOM/GRM observation of a bright burst from SGR 1E1841-045
- IPN triangulation of a bright burst from SGR 1E1841-045
- GRB 260429B / EP260429a: AstroSat CZTI detection
- SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
- GRB 260429A: Fermi GBM Detection
- EP260429a: EP-WXT detection of a fast X-ray transient
- GRB 260429A: Fermi GBM Final Real-time Localization
- Fermi GRB 260428A: Global MASTER-Net observations report
- IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
- Fermi GRB 260421C: Global MASTER-Net observations report
- Fermi GRB 260421B: Global MASTER-Net observations report
- GRB 260421B: LCO optical afterglow confirmation
- Fermi GRB 260417B: Global MASTER-Net observations report
- EP260417a: Global MASTER-Net observations report
- EP260416a: GMG Optical Observation
- Fermi GRB 260417A: Global MASTER-Net observations report
- GRB 260417A: AstroSat CZTI detection
- IPN triangulation of GRB 260411B
- EP260416a: Einstein Probe detection of an X-ray transient
- Fermi trigger No 797912738: Global MASTER-Net observations report
- EP260321a: CMO SAI J,K observations
- Fermi GRB 260412A: Global MASTER-Net observations report
- GRB260411B: 3.6m DOT optical observation
- Fermi trigger No 797039833: Global MASTER-Net observations report
- EP260403a: COLIBRÍ optical counterpart candidate
- EP260403a: Einstein Probe detection of an X-ray transient
- EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
- Fermi GRB 260401A: Global MASTER-Net observations report
- EP260329b: Mondy and Assy-Turgen optical upper limits
- EP260329b: GOTO detection of optical counterpart
- EP260329a: COLIBRÍ optical upper limit
- EP260329b: Global MASTER-Net observations report
- Fermi trigger No 796485221: Global MASTER-Net observations report
- EP 260329b: COLIBRÍ optical observations
- EP260329b: LCO optical observations of the counterpart
- EP-WXT trigger 01709259209: TRT optical counterpart detection
- EP260321A: Mondy optical observations