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"- GRB 260226A: LAST optical upper limit
- GRB 260226A: Fermi GBM observation
- GRB 260226A: Fermi-LAT refined analysis
- The EP-WXT trigger 01709258652 is likely a flaring star
- LAT GRB260226.44: Global MASTER-Net observations report
- Fermi GRB 260226A: Global MASTER-Net observations report
- GRB 260226A: AstroSat CZTI detection of bright long burst
- EP260214a: VLA 6 GHz detection
- GRB 260226A: Fermi-LAT detection of a bright burst
- GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
- EP260224a: LCO optical upper limits
- GRB260225A: SVOM/ECLAIRs refined position
- GRB 260226A: Fermi GBM Final Real-time Localization
- GRB 260225A: EP-FXT follow-up observation
- GRB 260225A: SVOM/VT optical observation
- GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
- GRB 260225C: Fermi GBM Final Real-time Localization
- GRB 260223A: Fermi GBM Observation
- GRB 260225A: SVOM/VT optical upper limits
- GRB 260225B: Fermi GBM Final Real-time Localization
- EP260126a: VLA 6 GHz detection
- EP260223a: Liverpool Telescope upper limits
- GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- GRB 260225A: SVOM detection of a burst
- EP260224a: Einstein Probe detection of an X-ray transient
- EP 260225.148: COLIBRÍ Confirmation of flaring star
- EP260223a: Xinglong optical upper limit
- The EP-WXT trigger 01709258631 is likely a flaring star
- GRB 260223A: Glowbug gamma-ray detection
- EP260213a: Mephisto optical upper limits
- EP260223a: EP-FXT follow-up observation
- sb26021801: SVOM/VT optical upper limits
- GRB 260223A: COLIBRÍ optical afterglow decay confirmation
- sb26021801: SVOM/C-GFT upper limit
- EP260223a: COLIBRÍ optical upper limits
- EP260223a: Einstein Probe detection of an X-ray transient
- GRB 260223A: SVOM/VT optical observation
- GRB 260223A: SVOM/GRM observation
- GRB 260223A: COLIBRÍ further optical observations and a brightening
- EP260221a: Optical upper limit with Kinder observations
- GRB 260223A: COLIBRÍ optical observations
- GRB 260223A: DDOTI Optical Candidate
- GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
- Fermi GRB 260223A: Global MASTER-Net observations report
- GRB 260223A: Fermi GBM Final Real-time Localization
- EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
- EP260221a: COLIBRÍ optical counterpart candidate
- EP260221a: Gemini South z-band upper limit
- GRB 260222A: Fermi GBM Final Real-time Localization
- EP260221a: Global MASTER-Net observations report
- EP260221a: EP-FXT follow-up observation
- Fermi GRB 260221B: Global MASTER-Net observations report
- GRB 260221B: Fermi GBM Final Real-time Localization
- EP-WXT01709258519: Xinglong optical upper limit
- EP260221a: Xinglong optical upper limit
- Fermi GRB 260221A: Global MASTER-Net observations report
- ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
- GRB 260221A: Fermi GBM Final Real-time Localization
- EP260221a: GOTO optical upper limit
- EP260221a: COLIBRÍ optical upper limit
- SVOM alert sb26021801: LCO optical upper limit
- EP260221a: Einstein Probe detection of an X-ray transient
- The EP-WXT trigger 01709258519 is likely caused by Mrk 421
- GRB 260219A: AstroSat CZTI detection
- IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260219A: GECAM-B observation of a long burst
- Fermi GRB 260219A: Global MASTER-Net observations report
- GRB 260219A: Fermi GBM Final Real-time Localization
- SVOM alert sb26021801: LAST optical upper limit
- sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- IceCube Alert 260217A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260217A
- GRB 260217A: Fermi GBM Final Localization
- GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
- sb26021801: SVOM detection of a long faint X-ray transient
- The EP-WXT trigger 01709258455 is likely a flaring star
- EP-WXT 01709258455: NOT optical upper limits
- EP260214b: Mondy optical observations
- EP260214b: 1.3m DFOT optical upper limit
- EP260210a: Mondy optical upper limits
- Konus-Wind detection of GRB 260212A
- GRB 260208A: AbAO and Terskol optical upper limits
- GRB 260208A: continued Mondy optical observations
- IPN triangulation of GRB 260212A
- IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260213A: GECAM-B observation of a short burst
- GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
- GRB 260216A: Fermi GBM Final Real-time Localization
- EP260214b: Liverpool Telescope optical observations
- GRB 260206A: probable hard X-ray burst from 4U 0513-40
- EP260214b: Optical upper limit with Kinder observations
- EP260214a: Optical upper limits with Kinder observations
- EP260214b: EP-FXT follow-up observation
- EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
- EP260214b: DDOTI Optical Detection
- EP260214b: GROWTH-India Telescope optical upper limit
- EP260214a: VLT near-infrared observation
- EP260214b: SVOM/VT optical observation
- EP260214a: NOT optical upper limits
- EP260214a: COLIBRÍ optical upper limits