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"21392 results found.
- GRB 250106A: NOT optical observations
- GRB 250103B: REM optical/NIR upper limits
- GRB 250101A: REM optical/NIR counterpart detection
- GRB 250106A: Swift-XRT observations
- GRB 250106A: SVOM/VT optical candidate
- GRB 250106A: Swift ToO observations
- GRB 241229A: SVOM/VT optical upperlimit
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103B: LCO/1m optical afterglow candidate detection
- GRB 250103A: Swift-XRT observations
- GRB 250101A: 1.3m DFOT optical afterglow detection
- GRB 241229A: 1.3m DFOT upper limit
- GRB 241228A: 1.3m DFOT upper limit
- GRB 250103B：SVOM/VT optical counterpart
- GRB 250101A: further LCOGT optical afterglow observations
- GRB 250103B: LCOGT Optical Upper Limit
- Swift GRB 250103B: Global MASTER-Net observations report
- GRB 250103A: Swift ToO observations
- GRB 250101a: Liverpool Telescope optical follow-up
- GRB 250103B: SVOM detection of a long burst
- GRB 250103B: Swift detection of a burst
- GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
- LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
- GRB 250101A: Swift-BAT refined analysis
- GRB 250101A: further SAO RAS optical observations
- GRB 250101A: LCO optical counterpart detection
- GRB 250101A NUTTelA-TAO / BSTI Early Measurements
- GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
- GRB 250101A: Swift/UVOT Detection
- GRB 250101A: 1.6m Mephisto multi-band optical followup
- GRB 250101A: Swift-XRT refined Analysis
- GRB 250101A: Montarrenti Observatory optical observations and rebrightening
- GRB 250101A: LCOGT optical afterglow detection
- GRB 250101A: OASDG optical observations
- GRB 250101A: BOOTES-4/MET optical afterglow detection
- GRB 250101A: SAO RAS optical observations
- GRB 250101A: Enhanced Swift-XRT position
- GRB 250101A: Xinglong-2.16m spectroscopic redshift
- GRB 250101A: SVOM/C-GFT early optical observations
- GRB 250101A: MASTER earlier OT observations with SOSS emission features
- GRB 250101A: Nanshan/HMT optical observations
- GRB 250101A : GIT optical detection
- GRB 250101A: Swift detection of a burst with an optical counterpart
- Swift GRB250101.56: Global MASTER-Net observations report
- EP241217a: VLA Radio Detection
- GRB 241229A: EP-FXT X-ray afterglow confirmation
- GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
- GRB 241229B: SVOM/GRM observation
- EP241217A: J band upper limit by SYSU 80cm telescope
- GRB 241228B: SAO RAS optical observations
- GRB 241229A: SAO RAS optical observations
- GRB 241229B: SVOM/VT optical candidate
- GRB 241229A: Swift-XRT observations
- Konus-Wind detection of GRB 241228A
- GRB 241229A: EP-FXT afterglow candidates
- GRB 240606B: 7DT Optical upper limits
- GRB 241229B: Swift-BAT refined analysis
- GRB241229B: UVOT upper limits
- GRB 241228B: D50 optical detection
- GRB 241228B: Fermi GBM Observation
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229B: Fermi GBM Observation
- GRB 241229A: Swift ToO observations
- GRB 241229B: NUTTelA-TAO / BSTI Optical Limits
- GRB 241229B: Swift-XRT refined Analysis
- Swift GRB 241229B: Global MASTER-Net observations report
- GRB 241228A: NOT optical upper limits
- GRB 241228A: Swift-BAT refined analysis
- GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
- GRB 241229B: Swift detection of a burst
- GRB 241228A: Fermi GBM Observation
- Swift GRB 241228A: Global MASTER-Net observations report
- GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
- GRB 241228A: GROWTH-India telescope optical upper limit
- GRB 241228B: Swift ToO observations
- GRB 241228A: Swift-XRT refined Analysis
- GRB 241228A: Swift/UVOT Upper Limits
- GRB 241228A: Enhanced Swift-XRT position
- GRB 241228A: Swift detection of a burst
- GRB 241223A: Swift-XRT observations
- GRB241113A: 7DT Optical upper limits
- GRB 241223A: GOTO optical observations summary
- GRB 241223A: Swift ToO observations
- GRB 241218A: Mondy AZT-33IK optical upper limit
- GRB 241218A: Swift/UVOT Upper Limits
- EP241217a: optical upper limit with the Liverpool Telescope
- GRB 241209B: EP-FXT afterglow detection
- GRB 241218A: NOT optical upper limits
- GRB 241218A: Swift-BAT refined analysis
- EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
- GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
- GRB 241218A: REM optical upper limit
- GRB 241217A/EP241217b: REM optical/NIR upper limits
- EP241217a: REM optical/NIR upper limits
- GRB 241218a: Liverpool Telescope optical follow-up
- GRB 241217a: Liverpool Telescope optical follow-up
- GRB 241218A: Swift-XRT refined Analysis
- GRB 241209A: ATCA radio follow-up observations
- GRB 241218A: LCOGT Optical Upper Limit
- GRB 241218A: Enhanced Swift-XRT position