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').
18174 results found.
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: Swift/UVOT Detection
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- GRB 250221A: REM optical/NIR afterglow detection
- GRB 250221A: Enhanced Swift-XRT position
- GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
- GRB 250221A: Swift detection of a burst with an optical counterpart
- Swift GRB250221.15: Global MASTER-Net OT detection
- Swift GRB250221.15: Global MASTER-Net observations report
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250219A: Swift-XRT observations
- GRB 250219A: Swift ToO observations
- GRB 250217C: Swift-XRT observations
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: Tiled Swift observations
- IPN triangulation of GRB 250217C (short)
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- GRB 250213A: Swift-XRT observations
- GRB 250215A / EP250215a: LCO detection of the afterglow
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: Fermi GBM Observation
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: Swift-XRT refined Analysis
- GRB 250213A: Swift ToO observations
- GRB 250211A: SVOM trigger sb25021103 is not a GRB
- GRB 250211A: Swift ToO observations
- GRB 250207A: Fermi GBM Observation
- Konus-Wind detection of GRB 250207A
- GRB 250207A: Skynet optical afterglow observations
- GRB 250207A: 1.3m DFOT Optical observations
- GRB 250206A: Swift-XRT observations
- GRB 250129A: GRANDMA Continued Afterglow Detection
- GRB 250207A: Swift-BAT refined analysis
- GRB 250205A: 1.3m DFOT optical upper limit
- GRB 250206A: Tiled Swift observations
- GRB 250206A: Fermi-LAT detection
- GRB 250207B: Swift-XRT observations
- EP250207a: EP-WXT detection and XRT follow-up observation
- GRB 250207A: Swift-XRT refined Analysis
- GRB 250207A: Enhanced Swift-XRT position
- GRB 250129A: ABObservatory SLOAN r’ afterglow detection
- GRB 250207A: REM IR afterglow detection
- GRB 250207A: FRAM-Auger optical detection
- GRB 250207B: Tiled Swift observations
- GRB 250207A: REM optical afterglow detection
- GRB 250207A: Swift/UVOT Detection
- GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
- GRB 250207A: Swift detection of a burst with optical counterpart
- GRB 250205A: Fermi GBM Observation
- GRB 250205A: Swift/UVOT Upper Limits
- GRB 250205A: Swift/XRT detection
- IPN triangulation of GRB 250201A
- GRB 250129A: Swift-BAT refined analysis
- IPN triangulation of GRB 250204B (short/hard)
- IPN triangulation of GRB 250202B
- GRB 250129A: LCO late afterglow detection
- GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
- GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
- GRB 250129A: SVOM/C-GFT optical observations
- Swift GRB250129A: MASTER 4 days observations report
- Konus-Wind detection of GRB 250129A
- GRB 250129A: 1.3m DFOT Optical observations
- GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
- GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
- GRB 250129A: COLIBRÍ Optical Observations
- GRB 250129A: TNG NIR afterglow detection
- GRB 250129A: GRANDMA/TAROT optical afterglow detection
- GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
- GRB 250128B: VLA radio upper limit
- Ep250125A: 1.3m DFOT optical upper limit
- GRB 250129A: Skynet optical observations
- GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
- GRB 250129A: Swift-XRT refined Analysis
- GRB 250128B: TNG optical upper limit
- GRB 250129A: Swift/UVOT Detection
- GRB 250127A: CrAO and Terskol optical upper limits
- GRB 250129A: Enhanced Swift-XRT position
- GRB 250128B: NOT optical upper limit
- GRB 250129A: REM optical/NIR afterglow detection
- GRB 250129A: Early afterglow detection by LCO.
- Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
- GRB 250129A: LCO optical observations
- GRB 250129A: GOTO optical observations show brightening afterglow
- Swift GRB 250129A: Global MASTER-Net observations report
- GRB 250128B: Enhanced Swift-XRT position
- GRB 250129A: Swift detection of a burst with an optical counterpart
- Swift GRB 250129A: Global MASTER-Net OT detection
- GRB 250128B: Swift-XRT refined Analysis
- GRB 250128B: Fermi GBM Observation
- GRB 250128B: GOTO optical upper limit
- Swift GRB 250128B: Global MASTER-Net observations report
- EP250125a: Upper limits from Swift/BAT-GUANO
- GRB 250128B: LCO optical observations
- GRB 250128B: Swift detection of a short burst
- GRB 250127A: Swift-XRT observations
- GRB 250127A: EP-FXT afterglow detection