GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"- EP260321a: uGMRT observations
- GRB 260407A: Fermi GBM Final Real-time Localization
- EP260405a: GMOS-N optical upper limits
- EP260405a: SVOM/VT optical upper limits
- EP260405a: Global MASTER-Net observations report
- EP260405a: Einstein Probe detection of a fast X-ray transient
- The EP-WXT trigger 01709259621 is likely a flaring star
- EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
- The EP-WXT trigger 01709259615 is likely a flaring star
- Fermi trigger No 797039833: Global MASTER-Net observations report
- GRB 260403A: GECAM-B observation of a long burst
- EP260324A / AT 2026hir: COLIBRÍ further optical observations
- Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
- EP260403a: refined analysis of the EP-WXT and EP-FXT observations
- The EP-WXT trigger 01709259586 is likely a flaring star
- GRB 260330B: SVOM/VT further optical observation
- Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
- GRB 260330B: SVOM/ECLAIRs refined analysis
- EP260403a: LCO optical observations of the counterpart
- GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
- EP260403a: LCO optical counterpart detection
- EP260403a: COLIBRÍ optical counterpart candidate
- GRB 260330B: SVOM/VT optical candidate
- EP260403a: Einstein Probe detection of an X-ray transient
- GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
- GRB 260403A: AstroSat CZTI detection
- EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260402B: GECAM-B observation
- EP260402a/GRB 260402A: Jinshan near-infrared upper limit
- GRB 260402C: NuSTAR detection of prompt emission
- GRB 260402C: AstroSat CZTI detection of a long burst
- EP260324A / AT 2026hir: COLIBRÍ optical observations
- GRB 260403A: Fermi GBM Final Real-time Localization
- EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
- GRB 260402B: Fermi GBM Final Real-time Localization
- GRB 260402A: WINTER J-band upper limit
- GRB260402A: GROWTH-India Telescope optical upper limit
- GRB 260402A / EP260402a: SVOM/VT optical upper limits
- EP260402a/GRB 260402A: SVOM/C-GFT upper limit
- GRB 260401A: SVOM/GRM observation
- GRB 260401A: GECAM-B observation
- EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
- GRB 260402A: Kilonova-Catcher optical upper limit
- GRB 260402A: MASTER optical observations
- GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 260402A: SVOM/MXT candidate X-ray afterglow
- GRB 260402A: SVOM detection of a burst
- Fermi GRB 260401A: Global MASTER-Net observations report
- GRB 260401A: Fermi GBM Observation
- GRB 260401A: NuSTAR detection of prompt emission
- GRB 260401A: CALET Gamma-Ray Burst Monitor detection
- GRB 260401A: MAXI/GSC detection
- GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
- GRB 260401A: Fermi GBM Final Real-time Localization
- EP260329b: Mondy and Assy-Turgen optical upper limits
- GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
- EP260321a :Xinglong optical observations
- EP260327a: Xinglong optical upper limit
- EP260329b: GOTO detection of optical counterpart
- GRB 260330B: SVOM/VT optical upper limits
- Konus-Wind detection of GRB 260320A
- Konus-Wind detection of GRB 260316B (duplicate submission)
- Konus-Wind detection of GRB 260316B
- GRB 260321A: SVOM/ECLAIRs refined analysis
- EP260329b: J-band upper limits with WINTER
- EP260329a: J-band upper limit with WINTER
- GRB 260330A: Glowbug gamma-ray detection
- GRB 260310A: VLA Multi-frequency Radio Observations
- Fermi GBM Sub-Threshold Detection of GRB 260330B
- GRB 260330B: LCO optical upper limits
- GRB 260330B: SVOM detection of a burst
- EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
- EP260329b: refined analysis of the EP-WXT and EP-FXT observations
- EP260329a: COLIBRÍ optical upper limit
- EP260329a: EP-FXT follow up observation
- EP260329a: NOT optical counterpart candidate
- GRB 260330A: Fermi GBM Final Real-time Localization
- EP260329b: Global MASTER-Net observations report
- Fermi trigger No 796485221: Global MASTER-Net observations report
- GRB 260327A: Insight-HXMT/HE detection
- EP260329b: Optical follow-up with Kinder observations
- EP 260329b: COLIBRÍ optical observations
- EP260329a: Optical upper limit with Kinder observations
- EP260329b: LCO optical observations of the counterpart
- GRB 260326A: Insight-HXMT/HE detection
- EP260329b: Einstein Probe detection of an X-ray transient
- EP260329a: Einstein Probe detection of an X-ray transient
- EP-WXT trigger 01709259209: TRT optical counterpart detection
- The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
- GRID detection of GRB 260326A
- GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
- EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260327a: SVOM/VT optical upper limits
- SMA Detection of GRB 260310A / AT 2026fgk
- GRB 260307B: ATCA Radio Upper Limits
- EP260327a: WINTER J-band upper limit
- EP260327a: COLIBRÍ optical upper limits
- GRB 260327A: AstroSat CZTI detection of a long burst
- EP260327a: Gemini-North optical upper limits
- EP260324a: GROWTH-India Telescope optical observation