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"12320 results found.
- GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
- Fermi trigger No 771424081: Global MASTER-Net observations report
- EP250612a: Global MASTER-Net observations report
- sb25061207: Swift-XRT observations
- EP250612a/GRB 250612B: JinShan optical upper limit
- EP250610a: Upper limit from Fermi-GBM Observations
- Swift GRB250612.04: Global MASTER-Net observations report
- GRB 250610B: Swift/UVOT Detection
- EP250610A: Swift/UVOT Upper limits
- EP250610a: TNG NIR upper limit
- EP250610a: Liverpool Telescope optical upper limits
- GRB 250610B: Swift-XRT counterpart detection
- GRB 250610B: GOTO optical upper limit
- EP250610a: Global MASTER-Net observations report
- GRB 250610B : SVOM/GWAC-F60A and F50 observations
- EP250610a: SVOM/VT optical upper limit
- EP250610a: Swift-XRT counterpart detection
- EP250610a: COLIBRÍ optical upper limit
- Fermi trigger No 771072240: Global MASTER-Net observations report
- GRB 250605A: Swift/UVOT Upper Limits
- GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
- GRB 250527C: CrAO Optical Upper Limit
- GRB 250605A: SVOM/VT optical upper limit
- Fermi GRB 250606A: Global MASTER-Net observations report
- Fermi trigger No 770867684: Global MASTER-Net observations report
- GRB 250605A: LT optical observations
- GRB 250605A: Swift detection of a burst
- Swift GRB250605.79: Global MASTER-Net observations report
- GRB 250601A: PRIME H band upper limit.
- GRB 250601A: PRIME J band upper limit.
- GRB 250603A: Swift/UVOT Upper Limits
- Fermi trigger No 770638414: Global MASTER-Net observations report
- Swift GRB250603.05: Global MASTER-Net observations report
- GRB 250602A: DDOTI Optical Upper Limit
- GRB 250601A: Swift/XRT candidate afterglow
- GRB 250601A: Swift-XRT observations
- Fermi GRB 250601A: Global MASTER-Net observations report
- Fermi trigger No 770470765: Global MASTER-Net observations report
- Fermi GRB 250531A: Global MASTER-Net observations report
- EP#01709177494: Swift-XRT counterpart detection of known source
- GRB 250530C: BOOTES-7 optical upper limit
- Swift GRB 250530C: Global MASTER-Net observations report
- GRB 250530C: Swift detection of a burst
- GRB 250530A: SVOM/VT optical upper limit
- GRB 250530A: Swift-XRT counterpart detection
- GRB 250527C: Swift/UVOT Upper Limits
- GRB 250527B: Swift-XRT observations
- EP250526a: SVOM/VT optical upper limit
- Fermi trigger No 770058372: Global MASTER-Net observations report
- Fermi trigger No 770047117: Global MASTER-Net observations report
- GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
- GRB 250314A: CIDER NB1008 upper limit
- EP250526a: COLIBRÍ optical upper limits
- EP250526a: Global MASTER-Net observations report
- EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
- Fermi GRB 250523A: Global MASTER-Net observations report
- Fermi trigger No 769611916: Global MASTER-Net observations report
- GRB 250521B: SVOM/VT optical upper limit
- Fermi GRB 250522B: Global MASTER-Net observations report
- EP#01709176612: Swift-XRT counterpart detection of flaring star
- Fermi GRB 250521D: Global MASTER-Net observations report
- Fermi trigger No 769533898: Global MASTER-Net observations report
- Fermi trigger No 769499303: Global MASTER-Net observations report
- GRB 250521D: DDOTI Optical Upper Limit
- GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250521A: DDOTI Optical Upper Limit
- GRB 250520A: Swift/UVOT Upper Limits
- GRB 250520A: J-band observations with WINTER
- GRB 250520A: Gemini-South optical observations
- GRB 250520A: COLIBRÍ optical upper limit
- GRB 250520A: DDOTI Optical Upper Limit
- GRB 250520A: GOTO optical upper limit
- GRB 250520A: Swift detection of a burst
- Swift GRB 250520A: Global MASTER-Net observations report
- GRB 250516A: COLIBRÍ optical upper limit
- Fermi GRB 250516A: Global MASTER-Net observations report
- GRB 250515A: Swift-XRT observations
- Swift GRB 250516A: Global MASTER-Net observations report
- GRB 250516A: Swift/UVOT Detection
- GRB 250515A: GOTO candidate optical counterpart
- MAXI GRB250515.65: Global MASTER-Net observations report
- Fermi trigger No 768922089: Global MASTER-Net observations report
- Fermi GRB 250512A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250506A
- EP250511a: Koshka Zeiss-1000 Optical Upper Limit
- EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
- EP250512a: Global MASTER-Net observations report
- EP250511a: FTW optical and NIR observations
- EP250511a: Mephisto optical upper limits
- EP250511a: Global MASTER-Net observations report
- EP250511a: BOOTES-5 optical upper limit
- EP250508a: Gemini NIR upper limits
- Fermi GRB 250510C: Global MASTER-Net observations report
- Fermi GRB 250510B: Global MASTER-Net observations report
- GRB 250510A: Swift-XRT observations
- GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250507A: J-band observations with WINTER
- Fermi GRB 250509A: Global MASTER-Net observations report
- Swift GRB 250509A: Global MASTER-Net observations report
- GRB 250506A: NOT optical upper limits