GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"- GRB 261011A: TRT optical afterglow detection
- GRB 261011A: GOTO optical counterpart detection
- GRB 261011A: Swift detection of an unusual burst
- GRB 261011A: SVOM detection of a long bright burst
- GRB 261010A: Enhanced Swift-XRT position
- EP261010a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
- GRB 261010A: possible optical afterglow detected with the 1.5m OSN
- GRB 261010A: NOT possible optical counterpart
- GRB 261010A: Swift detection of a burst
- GRB 261010A: Fermi GBM Final Real-time Localization
- EP261006a: Kilonova-Catcher optical follow-up and detection
- GRB 261001A: SVOM/GRM observation
- EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
- EP261010a: SVOM/VT optical upper limits
- EP261006a: Liverpool Telescope optical follow-up
- EP261010a: NOT optical upper limits
- EP261010a: Global MASTER-Net observations report
- EP261010a Einstein Probe detection of an X-ray transient
- GRB 261009A: Fermi GBM Final Real-time Localization
- GRB261007A: Lesedi optical afterglow detection
- EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
- EP261007b: SVOM/ECLAIRs Upper Limit
- GRB 261008A: GECAM-B observation
- EP261006a: Optical follow-up observations with MATCH
- EP261007b: J-band upper limit by SYSU 80cm infrared telescope
- EP261007b: Refined analysis of the EP-WXT and autonomous EP-FXT observations
- GRB 261007A: SVOM/ECLAIRs refined analysis
- EP261007b: SVOM/VT optical detection of the NOT transient
- GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
- EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
- GRB 261007A: Glowbug gamma-ray detection
- GRB 261008A: Fermi GBM Final Real-time Localization
- GRB 261007A: NOT optical observations
- EP261007b: NOT optical observations, variable source outside the FXT region
- GRB 261007A: SVOM/GRM observation
- EP261007b: SVOM/C-GFT optical upper limits
- EP261007b: J-band upper limit with WINTER
- The EP-WXT trigger 01709321008/EP261007b：Xinglong optical upper limit
- GRB 261007A / EP261007a: AstroSat CZTI detection
- GRB 261005A: GECAM-B observation
- EP261006a: Swift/XRT detection of the fading X-ray counterpart
- EP261007a/GRB 261007A：Xinglong optical observation
- GRB 261007A/EP261007a: Optical follow-up observations with Kinder
- EP261006a: Optical follow-up observations with Kinder
- EP261006a: Liverpool Telescope optical observations
- EP261006a: Early Optical Observations by WFST
- GRB 261007A / EP261007a: SVOM/VT optical observations
- GRB 261007A: Swift-XRT afterglow detection
- EP261007b: SVOM/VT optical upper limits
- GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
- EP261007b: Einstein Probe detection of an X-ray transient
- GRB 261007A / EP261007a: NuSTAR detection of prompt emission
- EP Alert 261007.63: Global MASTER-Net observations report
- GRB 261007A / EP261007a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
- GRB 261007A: Autonomous identification and follow-up of the counterpart to GRB 261007A by BTSbot with ZTF and P60/SEDM
- SVOM GRB261007.27: Global MASTER-Net observations report
- GRB 261007A: GROWTH-India Telescope optical observations
- GRB 261007A / EP261007a: TRT optical observations
- GRB 261007A: Swift ToO observations
- GRB 261007A: SVOM/C-GFT optical observations
- GRB 261007A / EP261007a: LCO optical observations
- GRB 261007B: Fermi GBM Final Real-time Localization
- SVOM GRB261007.23: Global MASTER-Net observations report
- GRB 261005B: Swift-BAT refined analysis
- EP261006a: NOT spectroscopy of a blue continuum
- GRB 261007A: WINTER J-band observations
- EP261006a: LT and NOT discovery of an optical counterpart
- GRB 261007A: Fermi GBM observation
- GRB 261007A / EP261007a: VLT/X-shooter spectroscopic redshift z = 2.101
- EP261007a/GRB 261007A: Einstein Probe detection of an X-ray transient
- EP261006a: SVOM/VT optical upper limits
- EP261006a: Einstein Probe detection of an X-ray transient
- GRB 261007A: KAIT optical counterpart candidate
- GRB 261007A: SVOM detection of a burst
- EP trigger 01709320985: SVOM/C-GFT optical upper limits
- GRB 261005B: Swift-XRT refined Analysis
- EP trigger 01709320985: Ondrejov D50 optical upper limits
- GRB 261005A: Glowbug gamma-ray detection
- GRB 261005B: Swift/UVOT Upper Limits
- GRB 261005B: J-band upper limit with WINTER
- GRB 261001A: GECAM-B observation of a likely long GRB
- GRB 261005B: Fermi GBM Observation
- GRB 261005B: Enhanced Swift-XRT position
- The EP-WXT trigger 01709320908 is likely a flaring star
- EP trigger 01709320908: Ondrejov D50 observation, fading star suggests stellar flare
- GRB 261005B: Swift detection of a burst
- GRB 261005A: Fermi GBM Final Real-time Localization
- GRB 261003A: Glowbug gamma-ray detection of a likely short burst
- GRB 261002A: Fermi GBM Final Localization
- EP#01709320865: Swift-XRT observations
- GRB 260930B: SVOM/GRM observation
- Konus-Wind detection of GRB 260919A / EP 260920a
- GRB 260921B: GECAM-B observation
- EP261003a: J-band upper limit with WINTER
- EP261003a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- GRB 260930B: GECAM-B detection of a burst
- EP261003a: COLIBRÍ optical upper limits
- Trigger_21915: Swift ToO observations (retracted)
- Fermi GRB 261003A: Global MASTER-Net observations report