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"12316 results found.
- EP260126a: Optical upper limit with Kinder observations
- EP260126a: Liverpool Telescope optical upper limits
- EP260126a: Further NOT optical upper limits
- EP260126a: COLIBRÍ optical upper limits
- EP260126a: NOT optical observations
- Fermi-LAT Gamma-ray Observations of IceCube-260125A
- GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
- Fermi GRB 260125B: Global MASTER-Net observations report
- GRB 260114A: SVOM/VT optical upper limits
- Swift GRB260122.97: Global MASTER-Net observations report
- EP260119a: Mondy and SAO RAS optical upper limits
- EP260119a: Xinglong optical upper limit
- Fermi GRB 260120C: Global MASTER-Net observations report
- GRB 260120B: Swift/UVOT Detection
- GRB 260120B: COLIBRÍ optical upper limits
- SVOM GRB260121.06: Global MASTER-Net observations report
- Swift GRB260120B: Global MASTER-Net observations report
- Fermi trigger No 790601190: Global MASTER-Net observations report
- Fermi trigger No 790570272: Global MASTER-Net observations report
- GRB 260114A: Swift/UVOT Upper Limits
- SVOM GRB260119.92: Global MASTER-Net observations report
- SVOM GRB260119.92: Global MASTER-Net observations report
- SVOM GRB260119.90: Global MASTER-Net observations report
- EP260119a: Global MASTER-Net observations report
- GRB 260117A: ZTSh optical upper limit
- Swift GRB260118.48: Global MASTER-Net observations report
- GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
- SVOM GRB260117.82: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260115A
- GRB 260117A: SVOM/C-GFT upper limit
- GRB 260117A: Swift-XRT observations
- EP 260116a: COLIBRÍ optical upper limit
- EP260116a: Liverpool Telescope upper limits
- EP260116A: 1.3m DFOT optical upper limit
- IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
- EP260116a: Global MASTER-Net observations report
- EP260116a: Xinglong optical upper limit
- GRB 260114A: VLT/HAWK-I further near-infrared upper limits
- IceCube Alert 260115.73: Global MASTER-Net observations report
- Fermi GRB 260115A: Global MASTER-Net observations report
- GRB 260114A: VLT/HAWK-I near-infrared upper limits
- Konus-Wind detection of GRB 260114A
- GRB 260114A: 6 GHz VLA observations
- GRB 260114A : MITSuME Akeno optical upper limits
- GRB 260114A: COLIBRÍ optical upper limits
- GRB 260114A: TNG NIR upper limit
- GRB 260114A: NOT optical observations
- Konus-Wind detection of GRB 251230A / EP251230a
- Swift GRB 260114A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260111A
- GRB 260114A: Swift detection of a short burst
- IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
- Swift GRB260113.43: Global MASTER-Net observations report
- EP260110a: NOT and GTC Optical and Near-Infrared Observations
- EP260110a: TRT optical upper limits
- GRB 260111A: Swift-XRT observations
- Swift Trigger 1439093: is probably not GRB 260113A
- GRB 260111A: COLIBRÍ optical afterglow candidate
- GRB 260111A: GOTO optical upper limits
- GRB 251230A: Mondy Optical Observations
- EP260110a: SVOM/VT optical upper limits
- IceCube Alert 260111A: Global MASTER-Net observations report
- EP260110a: Global MASTER-Net observations report
- Fermi GRB 260111A: Global MASTER-Net observations report
- Swift trigger 1436759 is not an astrophysical event
- EP260110a: KAIT optical upper limit
- EP 260110a: COLIBRÍ optical observations
- EP260110a: SVOM/C-GFT upper limit
- EP260110a: BOOTES-5/JGU optical upper limit
- GRB 260109C: LCO optical upper limits
- GRB 260109C: Kilonova-Catcher optical upper limit
- Swift Trigger 1434591: possible GRB 260109C
- Swift GRB 251230A: Global MASTER-Net OT detection
- Fermi GRB 260107A: Global MASTER-Net observations report
- GRB 260102A: AbAO optical observations
- Fermi GRB 260105A: Global MASTER-Net observations report
- EP260105a: FTW optical observations
- EP260104a: FTW optical observations
- FRB 20251229A: COLIBRÍ optical upper limits
- Fermi GRB 260105B: Global MASTER-Net observations report
- EP260105a: LCO Optical Upper limit
- EP260104a: Global MASTER-Net observations report
- GRB 260101A: COLIBRÍ optical upper limits
- EP260105a: Global MASTER-Net observations report
- GRB 260104A: COLIBRÍ optical upper limits
- Fermi GRB 260104B: Global MASTER-Net observations report
- Swift GRB 260104A: Global MASTER-Net observations report
- GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
- GRB 260101A: Swift/UVOT Detection
- Fermi-LAT Gamma-ray Observations of IceCube-251225A
- SVOM GRB260103.08: Global MASTER-Net observations report
- SVOM GRB260102A: Global MASTER-Net observations report
- GRB 260102A: EP-FXT follow-up observation
- EP260101a: Global MASTER-Net observations report
- GRB 260102A: LCO optical upper limits
- GRB 260102A: Swift-XRT observations
- Swift GRB 260101A: Global MASTER-Net observations report
- SVOM GRB251231.57: Global MASTER-Net observations report
- GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
- GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening