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"12312 results found.
- EP260221a: Xinglong optical upper limit
- Fermi GRB 260221A: Global MASTER-Net observations report
- EP260221a: GOTO optical upper limit
- EP260221a: COLIBRÍ optical upper limit
- SVOM alert sb26021801: LCO optical upper limit
- IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
- Fermi GRB 260219A: Global MASTER-Net observations report
- SVOM alert sb26021801: LAST optical upper limit
- sb26021801: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- IceCube Alert 260217A: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-260217A
- EP-WXT 01709258455: NOT optical upper limits
- EP260214b: 1.3m DFOT optical upper limit
- EP260210a: Mondy optical upper limits
- Konus-Wind detection of GRB 260212A
- GRB 260208A: AbAO and Terskol optical upper limits
- EP260214b: Optical upper limit with Kinder observations
- EP260214a: Optical upper limits with Kinder observations
- EP260214b: GROWTH-India Telescope optical upper limit
- EP260214a: NOT optical upper limits
- EP260214a: COLIBRÍ optical upper limits
- EP260214a: SVOM/VT optical upper limits
- EP260214a: Global MASTER-Net observations report
- EP260213a: Liverpool Telescope optical upper limits
- EP260213a: Global MASTER-Net observations report
- EP260213a: COLIBRÍ optical upper limits
- EP260213a: Optical upper limits with Kinder observations
- EP260213a: SVOM/VT optical upper limit
- EP260213a: Mondy R-band optical upper limit
- EP260213a: NUTTelA-TAO Early Optical Limits
- EP260213a: SVOM/C-GFT upper limit
- EP/WXT 01709258378: NOT optical upper limits
- GRB 260211A: GOTO optical upper limit
- Fermi GRB 260212A: Global MASTER-Net observations report
- GRB 260211A: LAST optical upper limit
- Konus-Wind detection of GRB 260207B
- GRB 260211A: LCO optical upper limits
- GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- Fermi trigger No 792537871: Global MASTER-Net observations report
- Konus-Wind detection of GRB 260209B
- GRB 260208A: Swift UVOT detection
- EP260209a: COLIBRÍ optical upper limit
- Fermi GRB 260210C: Global MASTER-Net observations report
- EP260209a: LCO optical upper limits
- EP260210a: Global MASTER-Net observations report
- EP260209a: Global MASTER-Net observations report
- EP260210a: Optical upper limits with Kinder observations
- EP260210a: SVOM/VT optical upper limit
- EP260210a: COLIBRÍ optical upper limit
- EP260210a: SVOM/C-GFT upper limit
- GRB 260204A: Swift-XRT afterglow detection
- Fermi GRB 260209A: Global MASTER-Net observations report
- GRB 260208B: Swift-XRT observations
- GRB 260204A: Swift/UVOT Upper Limits
- Fermi GRB 260208C: Global MASTER-Net observations report
- Fermi GRB 260208D: Global MASTER-Net observations report
- GRB 260208A: Swift-XRT observations
- LAT GRB 260208B: Global MASTER-Net observations report
- Fermi GRB 260208A: Global MASTER-Net observations report
- Fermi GRB 260207B: Global MASTER-Net observations report
- GRB 260206A: Swift-XRT observations
- Fermi trigger No 792135758: Global MASTER-Net observations report
- GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
- GRB 260204A: Swift-XRT observations
- GRB 260204A: LCO optical afterglow detection
- GRB 260204A : MASTER Global robotic net optical observations
- GRB 260204A: GOTO optical upper limit
- GRB 260204A: LCO optical upper limits
- EP260110a: Late GTC/EMIR near-infrared observations
- GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
- GRB 260131A/B: EP/FXT X-ray afterglow detection
- GRB 260131A: NOT spectroscopic redshift z = 1.434
- EP260131a: Liverpool Telescope optical upper limits
- EP260131a: Xinglong optical upper limit
- EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
- GRB 260131B: MAXI/GSC detection
- EP260128a / GRB 260128A: COLIBRÍ optical upper limit
- Fermi GRB 260130A: Global MASTER-Net observations report
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- Fermi GRB 260129A: Global MASTER-Net observations report
- GRB 260128B: LCO optical upper limits
- GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- EP260128a: J band upper limit by SYSU 80cm infrared telescope
- GRB 260127B: Swift-XRT observations
- EP260128a: Liverpool Telescope optical observations and possible counterpart
- EP260128a: LCO optical upper limits
- EP260128a: Global MASTER-Net observations report
- Fermi GRB 260127A: Global MASTER-Net observations report
- IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260127A: COLIBRÍ optical observations
- EP260126a: Seimei/TriCCS optical upper limit
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: SVOM/C-GFT optical observations
- Fermi GRB 260127B: Global MASTER-Net observations report
- Swift GRB 260127A: Global MASTER-Net observations report
- GRB 260125A: Swift-XRT observations
- EP260126a: Optical upper limit with Kinder observations
- EP260126a: Liverpool Telescope optical upper limits
- EP260126a: Further NOT optical upper limits
- EP260126a: COLIBRÍ optical upper limits