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"
23838 results found.
- EP250402a: Einstein Probe detection of a fast X-ray transient
- GRB 250402A: SVOM detection of a burst
- GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250329B: Swift/UVOT Upper Limit
- GRB 250329A: Swift/UVOT Upper Limit
- GRB 250327B: Swift/UVOT Detection
- GRB 250327A: Swift/UVOT Upper Limits
- GRB 250331E: SVOM/GRM observation
- GRB250331D: AbAO optical observations
- GRB 250331D: Fermi GBM observation
- GRB 250331C: Swift/UVOT Upper Limits
- GRB 250331B: Swift/UVOT Upper Limits
- GRB 250328A: AbAO AS-32 Optical Observations
- GRB 250331D: Swift-XRT observations
- GRB 250331C: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250330B: SVOM/GRM observation of a short burst
- Fermi GRB 250331E: Global MASTER-Net observations report
- Fermi GRB 250331D: Global MASTER-Net observations report
- GRB 250331E: Fermi GBM Final Real-time Localization
- GRB 250327A Swift-BAT refined analysis
- Fermi trigger No 765078057: Global MASTER-Net observations report
- GRB 250329B: CAHA 2.2m telescope optical limit
- GRB 250331D: Swift ToO observations
- Swift GRB 250331C: Global MASTER-Net observations report
- Swift GRB 250331B: Global MASTER-Net observations report
- GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
- GRB 250320C : SVOM detection of a burst through offline search
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250330A: VLT/FORS2 Afterglow Detection
- GRB20250327B: 45th Parallel Observatory upper limit
- GRB 250328A: Swift/UVOT Detection
- GRB 250328A: Swift-XRT refined Analysis
- SVOM/sb25033102 is a false trigger
- GRB 250330A: Fermi GBM Observation
- GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331D: Fermi GBM Final Real-time Localization
- GRB 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- GRB 250330A: SVOM/VT optical upper limit
- SVOM/sb25033102: SVOM detection of an X-ray transient
- Fermi GRB 250330B: Global MASTER-Net observations report
- GRB 250330B: Fermi GBM Final Real-time Localization
- Fermi GRB 250330A: Global MASTER-Net observations report
- GRB 250330A: BOOTES-7 early optical upper limit
- GRB 250330A: Swift/UVOT Upper Limits
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250328A: 1.6m Mephisto optical observations
- GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
- GRB 250330A: Fermi GBM Final Localization
- IceCube Alert 250330.35: Global MASTER-Net observations report
- GRB 250330A: VLT/FORS2 Optical Observations
- GRB 250330A: Prompt Swift-XRT position
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- Swift GRB250330.26: Global MASTER-Net observations report
- GRB 250329B: SVOM/C-GFT optical upper limit
- GRB 250329B: SVOM/VT optical upper limit
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
- GRB250329A: REM optical afterglow detection
- GRB 250329B: SVOM detection of a faint transient
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250328A: SVOM/C-GFT optical upper limit
- GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
- GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
- GRB 250329A: VLT/X-shooter redshift z = 2.921
- GRB 250329A: SVOM detection of a burst
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: MASTER detection of OT rebrightening
- GRB 250327B: LCO optical counterpart detection
- GRB 250328A: SVOM detection of a burst
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
- GRB 250327b: Liverpool Telescope optical observations
- GRB 250322A: GRANDMA/TNOT optical upper limits
- GRB 250327A: SVOM/VT upper limits on the XRT position
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250327B: Las Cumbres optical counterpart detection
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327B: 1.6m Mephisto optical observations
- GRB 250327B: NOT spectroscopic redshift z = 3.035
- GRB 250327A: Swift-XRT refined Analysis
- GRB 250327B: GOTO optical counterpart detection
- GRB 250327B: SAO RAS optical candidate
- GRB 250327B: SVOM detection of a burst
- GRB 250327A: J-band observations with WINTER
- GRB 250327A: SVOM/VT optical candidate
- GRB 250327A: Fermi GBM observation
- Fermi GRB 250327A: Global MASTER-Net observations report
- Swift GRB 250327A: Global MASTER-Net observations report
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- GRB 250327A: Swift detection of a burst
- GRB 250327A: Fermi GBM Final Real-time Localization
- Fermi trigger No 764700395: Global MASTER-Net observations report