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"- GRB 250516A: COLIBRÍ optical upper limit
- Konus-Wind detection of GRB 250516A
- GRB 250516B: NuSTAR Detection of the Prompt Emission
- EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
- Fermi GRB 250516A: Global MASTER-Net observations report
- GRB 250515A: Swift-XRT observations
- GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
- Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
- GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
- Swift GRB 250516A: Global MASTER-Net observations report
- GRB 250515A: 1.6m Mephisto optical detection
- GRB 250516A: AstroSat CZTI detection
- GRB 2500515A/GOTO25cqo: SVOM/VT optical blue color
- GRB 250516A: Fermi GBM Observation
- GRB 250516A: Swift-XRT refined Analysis
- GRB 250516A: Swift/UVOT Detection
- GRB 250515A: Swift ToO observations
- GRB 250516B: GECAM-B detection of a bright long burst
- GRB 250516A: Enhanced Swift-XRT position
- GRB 250516A: Swift detection of a burst
- GRB 250516A: Fermi GBM Final Real-time Localization
- GRB 250512B / EP250512a: SVOM/GRM analysis
- GRB 250515A: GOTO candidate optical counterpart
- MAXI GRB250515.65: Global MASTER-Net observations report
- GRB 250515A: Fermi GBM Final Localization
- GRB 250424A: COLIBRÍ detection of the associated supernova
- Konus-Wind detection of GRB 250512B / EP250512a
- GRB 250502A: TESS observations
- Fermi trigger No 768922089: Global MASTER-Net observations report
- GRB 250511A: GECAM-A detection of a short burst
- GRB 250509A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
- Fermi GRB 250512A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250506A
- 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
- EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
- EP250512a: Global MASTER-Net observations report
- EP250511a: FTW optical and NIR observations
- GRB 250512B/EP250512a: SVOM/VT optical fading
- GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
- EP250511a: Mephisto optical upper limits
- GRB 250507B: GRBAlpha detection
- GRB 250506A: GRBAlpha detection
- GRB 250512B: SVOM detection of a burst
- GRB 250507B: SVOM/GRM observation of a burst
- EP250512a: Einstein Probe detection of an X-ray transient
- GRB 250512A: Fermi GBM Final Real-time Localization
- EP250511a: REM optical/NIR observations
- EP250511a: Einstein Probe follow-up obsevation and refined analysis
- EP250511a: SVOM/VT optical candidate comfirmation
- EP250511a: Global MASTER-Net observations report
- 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
- Fermi GRB 250510C: Global MASTER-Net observations report
- Fermi GRB 250510B: Global MASTER-Net observations report
- GRB 250510C: Fermi GBM Final Real-time Localization
- GRB 250510A: Swift-XRT observations
- GRB 250509A: Fermi GBM Observation
- IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
- GRB 250510A: follow-up observation with EP-FXT
- GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250510B: Fermi GBM Final Localization
- 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 (duplicate submission)
- GRB 250507A: J-band observations with WINTER
- EP250508a: SVOM/VT optical candidate fading
- GRB 250509A: Enhanced Swift-XRT position
- GRB 250509A: Prompt enhanced Swift-XRT position
- Fermi GRB 250509A: Global MASTER-Net observations report
- Swift GRB 250509A: Global MASTER-Net observations report
- GRB 250509A: Swift detection of a burst
- GRB 250509A: Fermi GBM Final Real-time Localization
- GRB 250506A: NOT optical upper limits
- EP250508a: Liverpool Telescope optical upper limits
- EP250508a: follow-up observation with EP-FXT
- EP250508a: SVOM/VT optical candidate
- 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.
- GRB 250506A: GECAM detection
- EP250508a: REM optical/NIR observations
- GRB 250506A: Swift-XRT afterglow detection
- EP250508a: Global MASTER-Net observations report
- GRB 250506A: SVOM/VT optical upper limit
- 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