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"5621 results found.
- The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
- EP260822a: Global MASTER-Net observations report
- IceCube Alert 260825A: Global MASTER-Net observations report
- GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
- GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
- GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- GRB 260818B: SVOM/C-GFT optical upper limit
- IceCube Alert 260821A: Global MASTER-Net observations report
- GRB 260810A: SVOM/GRM observation
- GRB 260810A: Insight-HXMT/HE detection
- EP260812a: NOT and Liverpool Telescope upper limits:
- EP trigger #01709278129 (EP260812b?): NOT optical counterpart
- Fermi GBM Sub-Threshold Detection of GRB 260809A
- GRB 260810A: Glowbug gamma-ray detection
- GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
- GRB 260810A: AstroSat CZTI detection of a long burst
- GRB 260809A: SAO RAS optical observations
- GRB 260808B: SAO RAS optical observations
- GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
- GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
- GRB260809A: MAO/AZT-22 optical observations
- IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260808B: Liverpool Telescope optical observations
- EP260809a: COLIBRÍ optical observations
- Fermi GRB 260808A: Global MASTER-Net observations report
- GRB 260709A: cubesat Avion detection
- Fermi GRB 260805A: Global MASTER-Net observations report
- GRB 260805A: Fermi GBM Final Localization
- GRB 260804A: Fermi GBM Final Real-time Localization
- GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- Fermi-LAT Gamma-ray Observations of IceCube-260722A
- EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
- GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
- GRB 260705A: Retraction of optical counterpart
- GRB 260718A: EP-FXT follow-up observation
- Fermi trigger No 806104130: Global MASTER-Net observations report
- Fermi GRB 260718A: Global MASTER-Net observations report
- GRB 260709A: AstroSat CZTI detection
- GRB 260706A: ATCA detection of possible radio counterpart
- GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
- Fermi-LAT Gamma-ray Observations of IceCube-260712A
- IceCube-260708A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-260708A: One candidate from the Zwicky Transient Facility
- IceCube Alert 260709A: Global MASTER-Net observations report
- EP260707a (by EP-FXT): NOT optical upper limit
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- GRB 260707A: Fermi GBM Final Real-time Localization
- The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
- Fermi trigger No 804738310: Global MASTER-Net observations report
- Fermi GRB 260703A: Global MASTER-Net observations report
- Fermi trigger No 804552016: Global MASTER-Net observations report
- EP260626a: COLIBRÍ optical upper limit
- MASS-Cube (GRID 2.0) detection of GRB 260616B
- GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
- EP260618a: EP-FXT follow-up observation
- IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
- GRB260616C: MAXI/GSC detection
- EP260610b: MAO/AZT-22 optical observations
- EP260610a: COLIBRÍ optical upper limits
- EP260610a: Einstein Probe detection of a fast X-ray transient
- GRB 260609A: Fermi GBM Final Localization
- GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
- GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
- EP260603a: COLIBRÍ optical upper limit
- GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
- Fermi GRB 260604C: Global MASTER-Net observations report
- Fermi GRB 260604C: Global MASTER-Net observations report
- Fermi trigger No 802141998: Global MASTER-Net observations report
- SVOM GRB260603.23: Global MASTER-Net observations report
- Fermi GRB 260602B: Global MASTER-Net observations report
- Fermi GRB 260602B: Global MASTER-Net observations report
- EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
- Fermi GRB 260601A: Global MASTER-Net observations report
- Fermi trigger No 801900520: Global MASTER-Net observations report
- GRB 260531A: MAXI/GSC detection
- GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
- EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
- GRB 260522B: Fermi GBM Final Real-time Localization
- Fermi trigger No 801135305: Global MASTER-Net observations report
- Fermi GRB 260522A: Global MASTER-Net observations report
- GRB 260520B: Fermi GBM Final Localization
- GRB 260509A: SVOM/ECLAIRs refined analysis
- GRB 260509A: CrAO ZTSh optical upper limit
- GRB 260515A: CrAO ZTSh BVRI optical observations
- Fermi GRB 260516C: Global MASTER-Net observations report
- GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRID detection of GRB 260507A
- SVOM GRB 260515A: Global MASTER-Net observations report
- EP260507a: Xinglong Schmidt optical counterpart detection
- Fermi GRB 260512A: Global MASTER-Net observations report
- EP260512a: COLIBRÍ optical upper limits
- MASS-Cube (GRID 2.0) detection of GRB 260507A
- GRB 260511B: SAO RAS optical observations
- GRB 260511B: GOTO optical counterpart detection
- GRB 260511B: SVOM/VT optical observations
- Fermi GRB 260511A: Global MASTER-Net observations report
- GRB 260509A: Liverpool Telescope optical observations
- GRB 260509A: SVOM/VT optical candidate with VHF data