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"
24704 results found.
- GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
- The EP-WXT trigger 01709176612: SVOM/VT optical observations
- EP#01709176612: Swift-XRT counterpart detection of flaring star
- GRB 250521D: DDOTI Optical Upper Limit
- GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250521D: LAST tentative optical counterpart candidate
- GRB 250521A: DDOTI Optical Upper Limit
- GRB 250520A: VLT/FORS2 Optical Observation
- GRB 250502A: Tautenburg observations
- GRB 250520A: Swift/UVOT Upper Limits
- IPN triangulation of GRB 250516B
- GRB 250520A: J-band observations with WINTER
- GRB 250520A: Gemini-South optical observations
- GRB 250520A: Swift-XRT refined Analysis
- GRB 250520A: REM optical/NIR early observations
- GRB 250520A:SVOM/VT optical candidate
- GRB 250520A: COLIBRÍ optical upper limit
- GRB 250520A: DDOTI Optical Upper Limit
- GRB 250520A: AstroSat CZTI detection of a short burst
- GRB 250520A: Enhanced Swift-XRT position
- GRB 250520A: Swift detection of a burst
- GRB 250516A: Swift-BAT refined analysis
- GRB 250516A: COLIBRÍ optical upper limit
- EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
- GRB 250515A: Swift-XRT observations
- GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
- GRB 250515A: 1.6m Mephisto optical detection
- GRB 250516A: Fermi GBM Observation
- GRB 250516A: Swift-XRT refined Analysis
- GRB 250516A: Swift/UVOT Detection
- GRB 250516B: GECAM-B detection of a bright long burst
- GRB 250516A: Enhanced Swift-XRT position
- GRB 250516A: Swift detection of a burst
- MAXI GRB250515.65: Global MASTER-Net observations report
- GRB 250424A: COLIBRÍ detection of the associated supernova
- GRB 250502A: TESS observations
- GRB 250509A: Swift-BAT refined analysis
- Fermi GRB 250512A: Global MASTER-Net observations report
- EP250512a/GRB 250512B: REM optical/NIR observations
- EP250511a: Koshka Zeiss-1000 Optical Upper Limit
- GRB 250507B: AstroSat CZTI detection
- EP250511a: Gemini optical counterpart observation
- EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
- EP250511a: Mephisto optical upper limits
- GRB 250512B: SVOM detection of a burst
- EP250512a: Einstein Probe detection of an X-ray transient
- EP250511a: REM optical/NIR observations
- EP250511a: Einstein Probe follow-up obsevation and refined analysis
- EP250511a: COLIBRÍ optical counterpart candidate
- EP250511a: BOOTES-5 optical upper limit
- EP250511a: Einstein Probe detection of an X-ray transient
- EP250508a: Gemini NIR upper limits
- GRB 250510B: Fermi GBM Observation
- GRB 250510A: Swift-XRT observations
- GRB 250509A: Fermi GBM Observation
- IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
- GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250509A: Swift-XRT refined Analysis
- GRB 250510A: SVOM possible detection of a burst
- GRB 250507A: J-band observations with WINTER
- GRB 250509A: Enhanced Swift-XRT position
- GRB 250509A: Swift detection of a burst
- GRB 250506A: NOT optical upper limits
- EP250508a: Liverpool Telescope optical upper limits
- EP250508a: KAIT optical upper limit
- GRB 250507A: KAIT optical upper limit
- EP250508a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250505B: SVOM/GRM observation of a short burst
- GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- EP250508a: REM optical/NIR observations
- GRB 250506A: Swift-XRT afterglow detection
- EP250508a: COLIBRÍ Optical Limit
- EP250508a: Einstein Probe detection of an X-ray transient
- GRB 250507A: Swift-XRT refined Analysis
- IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250506A: Swift/UVOT Upper Limits
- GRB 250507A: follow-up observation with EP-FXT
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250507A: REM optical/NIR observations
- GRB 250507A: SVOM/VT optical upper limit
- GRB 250506A: Swift-XRT observations
- Fermi-LAT Gamma-ray Observations of IceCube-250506A
- GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
- GRB 250507A: SVOM detection of a long burst
- GRB 250506A: Mephisto optical upper limits
- GRB 250504A: EIRSAT-1 GMOD Detection
- GRB 250502A: Bassano Bresciano Observatory upper limit
- GRB 250506A: Xinglong 2.16m optical upper limit
- SVOM/sb25050601: EP-FXT observations
- GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
- GRB 250506A: REM optical/NIR upper limits
- GRB 250506A: Fermi GBM Observation
- GRB 250506A: Swift XRT observations and possible counterpart detection
- GRB 250506A: TRT optical observations
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
- GRB 250506A: SVOM detection of a burst
- GRB 250504A: Swift-BAT refined analysis
- GRB 250430A: Swift-BAT refined analysis