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"- EP261105a: Second EP-FXT follow-up observation
- GRB 261108C: SVOM/VT early optical upper limits
- GRB 261108C: LCO optical upper limits
- SVOM GRB261108.99: Global MASTER-Net observations report
- GRB 261108D: SVOM detection of an X-ray transient
- SVOM GRB261108.89: Global MASTER-Net observations report
- GRB 261108C: SVOM detection of a burst
- GRB 261108A: Fermi GBM Observation
- Konus-Wind detection of GRB 261024A
- GRB 261108B: Fermi GBM Final Localization Correction
- GRB 261108A: SVOM/C-GFT optical upper limit
- GRB 261108A: SVOM/VT optical upper limits
- Fermi trigger No 815809059: Global MASTER-Net observations report
- EP261105a: VLT/HAWK-I nIR detection
- GRB 261108A: LCO optical upper limits
- GRB 261108A: FRAM-Auger optical limits
- SVOM GRB261108.05: Global MASTER-Net observations report
- GRB 261103A: SVOM/VT optical upper limits
- GRB 261108A: SVOM detection of a burst
- GRB 261108A: Fermi GBM Final Real-time Localization
- EP-WXT trigger 01709322272 : SVOM/C-GFT confirmation of a stellar flare
- EP Alert 261106.89: Global MASTER-Net observations report
- GRB 261029C: SVOM/GRM detection of a short burst
- The EP-WXT trigger 01709322272 is likely a flaring star
- The EP-WXT trigger 01709322271 is likely a flaring star
- The EP-WXT trigger 01709322274 is likely a flaring star
- EP-WXT 01709322274: GOTO observations
- EP-WXT trigger 01709322274: Ondrejov D50 detection of a likely stellar flare
- GRB 261103A: SVOM/ECLAIRs refined analysis
- EP Alert 261106.58: Global MASTER-Net observations report
- EP261015a/SN 2026ahoa: spectroscopic redshift confirmation z=0.310
- Konus-Wind detection of GRB 261024D
- EP261105a: PRIME near-infrared upper limit
- Konus-Wind detection of GRB 261029C (short / bright)
- EP261105a: VLT/FORS2 optical detection
- EP Alert 261105.81: Global MASTER-Net observations report
- EP261105a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP261103a: refined WXT analysis and FXT follow-up observations
- GRB 261104A：EP-FXT follow-up observation
- EP261105a: Global MASTER-Net observations report
- GRB 261104A: DECam Detection of an Optical Counterpart Candidate
- GRB 261104A: SVOM/ECLAIRs refined analysis
- EP261105a: LCO optical upper limits
- GRB 261104A: SVOM/VT optical upper limits
- EP261105a: SVOM/VT optical candidate
- IPN triangulation of GRB 261029C (short / bright)
- IPN triangulation of GRB 261025B (short)
- GRB 261103A: SVOM/C-GFT optical upper limit
- IPN triangulation of GRB 261024A
- EP261105a: Einstein Probe detection of an X-ray transient
- GRB 261104A: LCO optical upper limits
- EP261015a/SN 2026ahoa: MMT optical counterpart detection
- SVOM GRB261104.86: Global MASTER-Net observations report
- EP241208a: SVOM/ECLAIRs refined analysis
- GRB 261104A: SVOM detection of burst
- GRB 260924A: CrAO ZTSh optical observations
- EP261103a: NTT optical observation
- GRB 261029A : MITSuME Akeno optical afterglow detection
- GRB 261030C: AstroSat CZTI detection
- EP261103a: SVOM/VT optical observation
- EP261103a: BOOTES-6/DPRT early optical upper limits
- EP261103a: NOT optical counterpart candidate
- EP261103a: Einstein Probe detection of an X-ray transient
- GRB 261029A: VST/OmegaCAM detection of the optical afterglow at 3 days
- EP Alert 261103.85: Global MASTER-Net observations report
- GRB 261029A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation
- GRB 261103A: LCO optical upper limits
- GRB 261103A: SVOM/ECLAIRs detection of a burst through on-ground search
- Konus-Wind detection of GRB 261029A
- EP Alert 261102.98: Global MASTER-Net observations report
- EP-WXT trigger 01709322206: confirmation of a stellar flare by BOOTES-5
- GRB 261029A: SAO RAS optical observations
- The EP-WXT trigger 01709322206 is likely a flaring star
- EP261015a/SN 2026ahoa: VLT/FORS2 discovery of a pre-peak type Ic-BL supernova at a tentative spectroscopic redshift z=0.31
- GRB 261102A: Fermi GBM Detection
- GRB 261029C: AstroSat CZTI detection of a short burst
- GRB 261102A: Fermi GBM Final Real-time Localization
- GRB 261101B: BALROG localization (Fermi Trigger 815240277 / GRB 261101651)
- GRB 261101B: Fermi GBM Final Real-time Localization
- EP261030a: EP-FXT follow-up observation
- EP261030a: GROWTH-India Telescope Upper Limit
- GRB 261101A: Fermi GBM Final Real-time Localization
- EP261030a: Global MASTER-Net observations report
- EP261030a: Einstein Probe detection of a fast X-ray transient
- GRB 261030A: Fermi GBM Detection
- Fermi GRB 261030B: Global MASTER-Net observations report
- GRB 261030B: Fermi GBM Final Real-time Localization
- GRB 261029A: SVOM/ECLAIRs refined analysis
- The EP-WXT trigger 01709321980: KAIT confirmation of a stellar flare
- GRB 261030A: BALROG localization (Fermi Trigger 815070447 / GRB 261030686)
- GRB 261030A: Fermi GBM Final Real-time Localization
- GRB 261029A / AT 2026ahaw: Optical upper limits from the PKU 60cm Telescope
- GRB 261029A: Glowbug gamma-ray detection
- GRB 261024D: SVOM/GRM observation
- GRB 261026A: Mondy, SAO RAS and Terskol optical observations
- GRB 261029A : SVOM/GWAC-F60 observations
- GRB 261029A: GECAM-B detection of a bright burst
- EP-WXT trigger 01709321980: confirmation of a stellar flare by BOOTES-5
- The EP-WXT trigger 01709321980 is likely a flaring star
- EP Alert 261030.22: Global MASTER-Net observations report