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"12335 results found.
- GRB 251003A: Mondy optical upper limit
- Fermi GRB 251013A: Global MASTER-Net observations report
- GRB 251011B: Swift/UVOT Upper Limits
- Fermi GRB 251011A: Global MASTER-Net observations report
- GRB 251007B: Swift/UVOT Upper Limits
- EP251006a: Global MASTER-Net observations report
- IceCube Alert 251008A: Global MASTER-Net observations report
- GRB 251007B: COLIBRÍ optical upper limit
- GRB 250917B: iTelescope T-26 upper limit
- EP250911a: Koshka Zeiss-1000 Optical Upper Limit
- GRB 251007A: AKO Optical Upper Limit
- GRB 251005C: PRIME J-band upper limit
- Swift GRB 251007B: Global MASTER-Net observations report
- GRB 251007B: SVOM/C-GFT upper limit
- Swift GRB 251007A: Global MASTER-Net observations report
- GRB 250702B/EP250702a: JWST/NIRCam Observations
- GRB 251006B: COLIBRÍ optical upper limit
- Fermi GRB 251006B: Global MASTER-Net observations report
- Fermi GRB 251006A: Global MASTER-Net observations report
- GRB 251005C: Swift/UVOT Upper Limits
- Swift GRB 251005A: Global MASTER-Net observations report
- GRB 251005C: GOTO optical upper limits
- Fermi trigger No 781367244: Global MASTER-Net observations report
- GRB 251005C: Swift detection of a burst
- GRB 251002A: NIR observations with WINTER
- GRB 251001B: NIR observations with WINTER
- GRB 251003A: Swift/UVOT Upper Limits
- EP250821a: iTelescope T-59 possible detection of the optical counterpart
- GRB 251002A: Swift-XRT afterglow detection
- GRB 251001B: AbAO optical upper limit
- GRB 251003A: Swift detection of a burst
- Swift GRB251003A: Global MASTER-Net observations report
- Fermi GRB 251002A: Global MASTER-Net observations report
- Swift GRB 251001B: Global MASTER-Net observations report
- Fermi GRB 250929A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250926A
- IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
- Fermi trigger No 780609036: Global MASTER-Net observations report
- IceCube Alert 250926.52: Global MASTER-Net observations report
- GRB 250925A: Swift/UVOT Upper Limits
- GRB 250925A: COLIBRÍ photometric redshift
- GRB 250925A: SVOM/GWAC-F60A upper limit
- GRB 250925A : MITSuME Akeno optical upper limits
- Fermi GRB 250926A: Global MASTER-Net observations report
- GRB 250925A: Leavitt Observatory optical upper limit
- GRB 250925A: GROWTH-India Telescope Upper Limits
- Swift GRB 250925A: Global MASTER-Net observations report
- GRB 250924A: 1.6m Mephisto optical upper limits
- GRB 250924A: Swift/UVOT Detection
- GRB 250924A: GROWTH-India Telescope Upper Limits
- Swift GRB 250924A: Global MASTER-Net observations report
- GRB 250920B: AbAO optical upper limits
- Konus-Wind detection of GRB 250920C
- EP250911a: e-MERLIN radio observations
- Fermi GRB 250922B: Global MASTER-Net observations report
- GRB 250920C: NIR observations with WINTER
- GRB 250920B: NIR observations with WINTER
- Fermi trigger No 780156732: Global MASTER-Net observations report
- GRB 250916A: Swift/UVOT Detection
- GRB 250920B: Kitab-ISON optical upper limit
- GRB 250917B: KAIT optical upper limit
- GRB 250920C: Swift/UVOT Detection
- Swift GRB 250920C: Global MASTER-Net observations report
- GRB 250920B: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
- Swift GRB 250920B: Global MASTER-Net observations report
- Fermi GRB 250918A: Global MASTER-Net observations report
- GRB 250919A: Swift-XRT afterglow detection
- EP250919a: Global MASTER-Net observations report
- Fermi GRB 250919A: Global MASTER-Net observations report
- GRB 250917B: Swift/UVOT Upper Limits
- GRB 250916A: Swift-XRT observations
- GRB 250917B: Swift-XRT observations
- Fermi GRB 250917B: Global MASTER-Net observations report
- GRB 250917B: Swift detection of a short burst
- GRB 250916A: GOTO optical counterpart candidate
- Fermi GRB 250916A: Global MASTER-Net observations report
- GRB 250912A: Swift-XRT observations
- GRB 250912A: VLT observations
- GRB 250912A:SVOM/VT optical upper limit
- GRB 250912A: LCO optical upper limit
- Fermi GRB 250912A: Global MASTER-Net observations report
- EP250911a: Global MASTER-Net observations report
- IceCube-Cascade 250911A: Upper limits from a search for additional neutrino events in IceCube
- EP250911a: Upper limit from Fermi-GBM Observations
- EP250911a: Swift-XRT observations
- GRB 250911A: Swift/UVOT Detection
- Fermi GRB 250910B: Global MASTER-Net observations report
- EP250910a: Global MASTER-Net observations report
- GRB 250910A: SVOM/VT optical upper limit
- GRB 250910A: LCO optical upper limit
- EP#01709240653: Swift-XRT observations
- EP250908c: Global MASTER-Net observations report
- Fermi GRB 250909A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250905A
- IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
- EP250905a: Liverpool Telescope i-band upper limits
- EP250905a: Liverpool Telescope observations
- EP250905b: Global MASTER-Net observations report
- IceCube Alert 250905.84: Global MASTER-Net observations report