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"20955 results found.
- GRB 250419A: Optical Observations via Virtual Telescope Project
- EP250421a: REM optical upper limit
- EP250421a: Swift/XRT counterpart detection
- EP250421A: COLIBRÍ Optical Upper Limit
- GRB 250419A: Mondy Continued Optical Observations
- Fermi GRB 250421A: Global MASTER-Net observations report
- EP250421a: Global MASTER-Net observations report
- EP250421a: Mephisto optical counterpart confirmation
- IceCube Alert 250421.71: Global MASTER-Net observations report
- EP250421a: JinShan likely optical counterpart
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250419A: Liverpool Telescope observations
- GRB 250419A: LCO optical observation
- GRB 250419A: JinShan optical observations
- GRB 250419A: SVOM/VT optical continuous observations
- GRB 250419A: SVOM/C-GFT optical observations
- GRB 250419A: Swift/UVOT Follow up
- GRB 250419A: LCO optical afterglow multi-band observations
- GRB 250419A: Mondy and AbAO Optical Observations
- GRB 250419A: Liverpool Telescope observations
- GRB 250419A: AKO Optical Afterglow Detection
- GRB 250419A: MASTER optical afterglow observation
- Fermi-LAT Gamma-ray Observations of IceCube-250416A
- GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
- GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
- GRB 250419A: GOTO optical counterpart detection
- GRB 250419A: KAIT optical afterglow observations
- GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- EP250416a: Swift/XRT counterpart fading
- EP250416a: refined EP-WXT and EP-FXT analysis
- EP20250416a: Swift/XRT counterpart detection
- GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
- IceCube-250416A: DDOTI Optical Observations
- EP250416a: Gemini South-GMOS optical counterpart
- EP250225a: SVOM/VT optical brightening
- EP250416a: GSP optical upper limit
- EP250416a: Global MASTER-Net observations report
- IceCube-250416A: Global MASTER-Net observations report
- IceCube 250414.324: DDOTI Optical Observations
- EP250304a: ATCA radio observations
- EP250404a: Nanshan 0.43m Telescope optical observatios
- Fermi trigger No 766148493: Global MASTER-Net observations report
- Fermi trigger No 766173972: Global MASTER-Net observations report
- GRB 250411A: DDOTI Optical Observations
- Fermi GRB 250411A: Global MASTER-Net observations report
- GRB 250407A: Continued KAIT/Nickel optical observations
- GRB 250314A: e-MERLIN observations
- GRB 250407A: Mondy and AbAO Optical Observations
- EP250227a: Further NOT optical observations
- IceCube-250406A: Swift-XRT observations
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
- EP250407a: Global MASTER-Net observations report
- GRB 250407A: LCO detection of a fading optical counterpart
- Fermi-LAT gamma-ray observations of IceCube-250406A
- EP250407a: Swift-XRT observations
- EP250407a: EP-WXT detection of a fast X-ray transient
- GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250407A: KAIT Optical Afterglow Candidate
- IceCube-250406A: No candidates from the Zwicky Transient Facility
- GRB 250407A: Swift-XRT afterglow detection
- Fermi GRB 250407A: Global MASTER-Net observations report
- GRB 250407A: Swift ToO observations
- IceCube 250406A: DDOTI Optical Observations of the Refined Position
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- IceCube 250406.951: DDOTI Optical Observations
- IceCube Alert 250406.95: Global MASTER-Net observations report
- Fermi trigger No 765663719: Global MASTER-Net observations report
- EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
- Fermi GRB 250406A: Global MASTER-Net observations report
- GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- Fermi trigger No 765619921: Global MASTER-Net observations report
- GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
- EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
- GRB 250404A / EP250404a: Mondy optical observations
- EP250404a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- EP250402a: Optical upper limit with PD 1.3m observations
- GRB 250404A / EP250404a: NOT optical observations
- GRB 250331D: Swift-XRT afterglow detection
- EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
- EP250404a: REM optical/NIR observations
- EP250404a: Seimei/TriCCS optical counterpart detection
- EP250404A: COLIBRÍ/DDRAGO Optical Observations
- EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
- EP250404a: LCO optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- GRB 250403A: Montarrenti Observatory optical detection
- EP250404a: Global MASTER-Net observations report
- GRB 250403A: KAIT optical observations
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- GRB 250403A: Fermi GBM observations
- EP250404a: Mephisto multi-band optical detection
- EP250321A: J band upper limit by SYSU 80cm telescope
- EP250404a: Nanshan/HMT optical counterpart detection
- GRB 250402A: Mondy optical observations
- EP250402a: Optical upper limit with Kinder observations