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: 1.3m DFOT optical upper limit
- GRB 261010A: Pan-STARRS z-band imaging and upper limit
- EP261015a: SVOM/VT optical observation
- EP241111a and EP250125a: Upper limits from SVOM/GRM Observations
- GRB 261010A: VLA radio observations
- EP261015a: COLIBRÍ optical observations
- EP261015c: Einstein Probe detection of a fast X-ray transient
- EP261015b: Einstein Probe detection of an X-ray transient
- GRB261010A: Keck/MOSFIRE detection of a near-IR source
- EP261015a: Einstein Probe detection of a fast X-ray transient
- EP261015a (WXT 11900947714): Possible optical counterpart from NOT and LCO
- The EP-WXT trigger 01709321333 is likely a flaring star
- GRB 261010A: ASKAP non-detection of a radio afterglow
- GRB 261010A: LBT tentative near-infrared detection
- GRB 261011A: SAO RAS and AbAO optical observations
- GRB 261010A: Glowbug gamma-ray detection
- GRB 261008A: SVOM/GRM observation
- GRB 261009A: GECAM-B detection of a burst
- EP261006a : MeerKAT radio observations.
- IceCube-261012A: Upper limits from a search for additional neutrino events in IceCube
- GRB 261010A: initial pulse rest-frame energetics from Konus-Wind detection
- GRB 261010A: a short minimum variability timescale and a distinct pulse evolution compatible with a merger origin
- GRB 261013A: Fermi GBM Final Real-time Localization
- GRB 261011A: Later-epoch J-band upper limit from the SYSU 80 cm infrared telescope
- Fermi-LAT Gamma-ray Observations of IceCube-261012A
- GRID detection of GRB 261010A
- GRB 261011A: GECAM-B observation
- GRB 261011B: GECAM-B observation
- GRB 261010A: J-band upper limit by the SYSU 80cm infrared telescope
- IceCube-260919A: No transient candidates from the Zwicky Transient Facility
- GRB 261010A: Swift-XRT refined Analysis
- GRB 261011A: Swift-XRT refined Analysis
- GRB 261011A: Enhanced Swift-XRT position
- GRB 261010A: a Type I-L (merger-driven) GRB candidate
- GRB 261011A: 10.4m GTC spectroscopic redshift (z = 2.407)
- GRB 261011A: Swift-BAT refined analysis
- IceCube-261012A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 261010A: 10.4m GTC spectroscopy of the galaxy 2" from the afterglow
- MAXI GRB261012.23: Global MASTER-Net observations report
- GRB 261011A: REM optical/NIR observations
- Konus-Wind detection of GRB 261010A
- Konus-Wind detection of GRB 261011A
- Konus-Wind detection of GRB 261007A/EP261007a
- GRB 261011A: SOAR optical afterglow observations at ~17 hours
- EP261006a: 10 GHz VLA observations
- GRB 261011A: VLT/X-shooter redshift constraints
- GRB 261012A: MAXI GSC detection
- GRB 261010A: Swift-BAT refined analysis
- GRB 261011A : MITSuME Akeno optical afterglow candidate detection
- GRB 261011A: Optical followup from Sichuan South Observatory
- GRB 261011A: GMG Optical Observation
- GRB 261011A: Liverpool Telescope optical observations
- GRB 261011A: J-band observations by the SYSU 80cm infrared telescope
- GRB 261010A: NOT confirmation of the optical afterglow
- GRB 261010A: Fermi GBM Observation
- GRB 261011B: Fermi GBM Final Localization
- GRB 261011A: continued LCO optical observations
- EP261007b: Global MASTER-Net observations report
- GRB 261011A: GROWTH-India Telescope optical observations
- GRB 261011A: Luminance-band upper limit from a 28cm telescope in Chengde
- Swift GRB 261011A: Global MASTER-Net observations report
- GRB 261011A: Optical follow-up observations with Kinder
- GRB 261011A: SVOM/C-GFT optical observations
- EP261007b: Second EP-FXT follow-up observation and a possible X-ray counterpart to the optical transient
- GRB 261011A: LCO optical observations
- GRB 261011A: SVOM/VT optical observation from VHF data
- GRB 261011A: LCO optical observations
- 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