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 230428A: Fermi GBM Final Real-time Localization
- GRB 230427A: GIT optical upper limit
- GRB 230427A: Bassano Bresciano Observatory upper limit
- GRB 230427A: GMG upper limit
- GRB 230427A : OHP/T193 optical upper limit
- GRB 230427A: BOOTES-5/JGT afterglow detection
- GRB 230423A(trigger #1165354): Swift-BAT refined analysis
- GRB 230427A: AKO Upper Limit
- Swift GRB230427.44: Global MASTER-Net observations report
- GRB 230426A: MASTER OT J023135.16-792104.8 optical counterpart discovery
- GRB 230427A: MITSuME Akeno optical upper limits
- GRB 230426A: Fermi GBM Detection
- GRB 230427A: Enhanced Swift-XRT position
- GRB 230427A: Swift detection of a burst with an optical counterpart
- GRB 230426A: AstroSat CZTI detection
- Fermi trigger No 704233744: Global MASTER-Net observations report
- GRB 230426A: Fermi GBM Final Real-time Localization
- GRB 230423A: Swift/UVOT Upper Limits
- GRB 230425A: Fermi GBM Final Real-time Localization
- GRB 230423A: Swift-XRT refined Analysis
- GRB 230420A: Lowell Discovery Telescope Optical Detection
- GRB 230423A: Swift-XRT afterglow detection
- Erroneous submission
- Swift Trigger 1165354 is probably not a GRB
- GRB 221009A: Late-time JWST Observations and Detection of Supernova Emission
- GRB 230421A: Fermi GBM observation
- Konus-Wind detection of GRB 230418A
- GRB 230420A: Swift/UVOT Upper Limits
- GRB 230421: Swift/BAT-GUANO arcminute localization
- GRB230420A: VLT optical observation
- GRB 230420A: Swift-BAT refined analysis
- Duplicate of GCN 33668
- GRB 230421A: Fermi GBM Final Real-time Localization
- GRB 230420A: Swift-XRT refined Analysis
- GRB 230420A: MITSuME Akeno optical observation
- GRB 230420A: NOT optical afterglow confirmation
- GRB 230420A: Gaoyazi/GOT optical upper limit
- GRB 230420A: BOOTES-5/JGT optical afterglow detection
- GRB 230420A: LCOGT Optical Upper Limit
- GRB 230420A: Enhanced Swift-XRT position
- GRB230414B: VIRT Optical Upper Limit
- IPN triangulation of GRB 230418A (short)
- GRB 230420A: Swift detection of a burst
- GRB 230418A: AstroSat CZTI detection
- GRB 230418A: AGILE detection
- GRB 230402A: Fermi GBM detection
- GRB 230419A: Fermi GBM Final Real-time Localization
- GRB 230418A: Swift/BAT-GUANO detection outside the coded FOV
- GRB 230418A: Fermi GBM Observation
- IceCube-Cascade 230417A: Upper limits from a search for additional neutrino events in IceCube
- GRB 230402A: Fermi-LAT detection
- Fermi-LAT gamma-ray observations of IceCube-230416A
- GRB 230414B: Nickel and KAIT telescope optical observations
- Duplicate of GCN 33640
- Duplicate of GCN 33640
- GRB 230414B Swift-BAT refined analysis
- Duplicate of GCN 33642
- GRB 230415A: Fermi GBM detection
- GRB 230414B: Swift/UVOT Detection
- GRB 230414B: Osservatorio Astronomico Nastro Verde - Sorrento: optical observations
- IceCube-230416A: Upper limits from a search for additional neutrino events in IceCube
- GRB 230415A: Swift/BAT-GUANO detection
- New GCN Circulars Portal for Rapid Communications on Astronomical Transients is Online
- VIRT optical transient detection
- GRB 230414B: 3.6m DOT Optical observations, slow decay at early epochs
- GRB 230307A: iTelescope optical upper limit (likely)
- GRB 230414B: Montarrenti Observatory late time optical afterglow detection
- IceCube-230416A: IceCube observation of a high-energy neutrino candidate
- Fermi trigger No 703284533: Global MASTER-Net observations report
- GRB 230414B: Lulin 40cm-SLT optical limit
- GRB 230414B: Bassano Bresciano Observatory optical observations
- GRB 230414B: Redshift from OSIRIS/GTC
- GRB 230414B: AbAO optical observations
- GRB 230409B: 3.6m DOT near-infrared detection, afterglow confirmation
- GRB 230414B: Swift-XRT refined Analysis
- GRB 230414B: Dabancheng/GHOST optical observations
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230414A
- GRB 230414B: slow optical light curve decay
- GRB 230414B: SAO RAS optical observations
- GRB 230414B: Enhanced Swift-XRT position
- GRB 230414B: 1.3m DFOT Optical observations
- Fermi GRB 230414A: Global MASTER-Net observations report
- GRB 230414B: GROWTH India Telescope afterglow confirmation
- GRB 230414B (correction GRB name in the GCN 33615): Mondy optical afterglow candidate
- GRB 230414B: Nanshan/HMT optical afterglow detection
- GRB 230414A: Mondy optical afterglow candidate
- Swift GRB 230414B: Global MASTER-Net observations report
- GRB 230414B: Prompt enhanced Swift-XRT position
- GRB 230414B: Swift detection of a burst
- IceCube-230405A: BOOTES-4/MET Optical Upper Limits
- GRB 230414A: Fermi GBM Final Real-time Localization
- GRB 230328B: redshift lower limit estimating
- GRB 230409B: Mondy optical upper limit
- GRB 230409B: OHP/T193 optical upper limit
- GRB 230410B: VZLUSAT-2 detection
- GRB 230409D: VZLUSAT-2 detection
- GRB 230410B: AGILE detection of a burst
- GRB 230410A: Fermi GBM Final Real-time Localization
- Fermi GRB 230409C: Global MASTER-Net observations report
- Fermi GRB 230409A: Global MASTER-Net observations report