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.
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"19089 results found.
- EP260221a: Optical upper limit with Kinder observations
- GRB 260223A: COLIBRÍ optical observations
- GRB 260223A: DDOTI Optical Candidate
- EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
- EP260221a: COLIBRÍ optical counterpart candidate
- EP260221a: Gemini South z-band upper limit
- EP260221a: EP-FXT follow-up observation
- EP-WXT01709258519: Xinglong optical upper limit
- EP260221a: Xinglong optical upper limit
- ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
- 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
- SVOM alert sb26021801: LAST optical upper limit
- sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
- 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
- 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
- EP260214b: DDOTI Optical Detection
- EP260214b: GROWTH-India Telescope optical upper limit
- EP260214a: VLT near-infrared observation
- EP260214a: NOT optical upper limits
- EP260214a: COLIBRÍ optical upper limits
- EP260214b: OHP/T120 optical observations
- EP260214a: refined analysis of the EP-FXT observation
- EP260214b: LCO optical counterpart detection
- EP260214b: COLIBRÍ optical observations
- EP260214b: NOT optical counterpart detection
- EP260214b: Einstein Probe detection of a fast X-ray transient
- EP260214a: Einstein Probe detection of an X-ray transient
- EP260213a: Liverpool Telescope optical upper limits
- EP260213a: COLIBRÍ optical upper limits
- EP260213a: Optical upper limits with Kinder observations
- EP260213a: Mondy R-band optical upper limit
- EP260213a: SVOM/C-GFT upper limit
- EP260213a: refined analysis of the EP-FXT observation
- EP260213a: Einstein Probe detection of a fast X-ray transient
- EP/WXT 01709258378: NOT optical upper limits
- GRB 260212A: SVOM/GRM observation of a long burst
- GRB 260211A: LAST optical upper limit
- GRB 260210A: SVOM/GRM observation
- GRB 260211A: LCO optical upper limits
- GRB260131A/B: 3.6m DOT Optical Observations
- GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- EP260209a: COLIBRÍ optical upper limit
- EP260209a: LCO optical upper limits
- EP260210a: refined analysis of the EP-FXT observation
- GRB 260208A: LCO detection of the optical counterpart
- EP260209a: Einstein Probe detection of a fast X-ray transient
- EP260210a: Optical upper limits with Kinder observations
- GRB 260208C: AstroSat CZTI detection
- EP260210a: COLIBRÍ optical upper limit
- EP260210a: SVOM/C-GFT upper limit
- EP260210a: Einstein Probe detection of an X-ray transient
- GRB 260207B: AstroSat CZTI detection
- GRB 260208C: SVOM/GRM observation
- GRB 260204A: Swift-XRT afterglow detection
- GRB260208A: Liverpool Telescope optical follow-up observations
- GRB 260131A/B: continued Mondy optical observations
- GRB 260204A: Swift/UVOT Upper Limits
- GRB 260208B: COLIBRÍ optical observations
- GRB 260208A: Mondy optical observations
- GRB 260208A: 1.3m DFOT optical detection
- GRB 260208A: COLIBRÍ optical observations
- GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
- GRB 260208A: SVOM/VT optical observation
- GRB 260208D: Fermi GBM Final Real-time Localization
- GRB 260208B: Swift ToO observations
- GRB 260208B: SVOM/GRM observation of a bright burst
- GRB 260208C: Fermi GBM Final Real-time Localization
- GRB 260208A: Swift ToO observations
- GRB 260208B: Fermi GBM Final Real-time Localization
- GRB 260208A: Fermi GBM Final Real-time Localization
- GRB 260131A/B: Mondy and Terskol optical observations
- GRB 260206A: Tiled Swift observations
- GRB 260204A: Swift-XRT observations
- GRB 260204A: SVOM/VT optical candidate
- GRB 260204A : MASTER Global robotic net optical observations
- GRB 260204A: LCO optical upper limits
- EP260110a: Late GTC/EMIR near-infrared observations
- GRB 260131A: KAIT optical observations
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
- GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
- EP260131a: Liverpool Telescope optical upper limits
- EP260131a: COLIBRÍ further observations
- EP260131a: SVOM/VT optical observation