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.
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"- Fermi GRB 260223A: Global MASTER-Net observations report
- GRB 260223A: Fermi GBM Final Real-time Localization
- EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
- EP260221a: COLIBRÍ optical counterpart candidate
- EP260221a: Gemini South z-band upper limit
- GRB 260222A: Fermi GBM Final Real-time Localization
- EP260221a: Global MASTER-Net observations report
- EP260221a: EP-FXT follow-up observation
- Fermi GRB 260221B: Global MASTER-Net observations report
- GRB 260221B: Fermi GBM Final Real-time Localization
- EP-WXT01709258519: Xinglong optical upper limit
- EP260221a: Xinglong optical upper limit
- Fermi GRB 260221A: Global MASTER-Net observations report
- ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
- GRB 260221A: Fermi GBM Final Real-time Localization
- EP260221a: GOTO optical upper limit
- EP260221a: COLIBRÍ optical upper limit
- SVOM alert sb26021801: LCO optical upper limit
- EP260221a: Einstein Probe detection of an X-ray transient
- The EP-WXT trigger 01709258519 is likely caused by Mrk 421
- GRB 260219A: AstroSat CZTI detection
- IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260219A: GECAM-B observation of a long burst
- Fermi GRB 260219A: Global MASTER-Net observations report
- GRB 260219A: Fermi GBM Final Real-time Localization
- 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
- GRB 260217A: Fermi GBM Final Localization
- GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
- sb26021801: SVOM detection of a long faint X-ray transient
- The EP-WXT trigger 01709258455 is likely a flaring star
- EP-WXT 01709258455: NOT optical upper limits
- EP260214b: Mondy optical observations
- 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
- GRB 260208A: continued Mondy optical observations
- IPN triangulation of GRB 260212A
- IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260213A: GECAM-B observation of a short burst
- GRB 260216A: Fermi Gamma-ray Burst Monitor trigger 792969362/260216886 is not a GRB
- GRB 260216A: Fermi GBM Final Real-time Localization
- EP260214b: Liverpool Telescope optical observations
- GRB 260206A: probable hard X-ray burst from 4U 0513-40
- EP260214b: Optical upper limit with Kinder observations
- EP260214a: Optical upper limits with Kinder observations
- EP260214b: EP-FXT follow-up observation
- EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
- EP260214b: DDOTI Optical Detection
- EP260214b: GROWTH-India Telescope optical upper limit
- EP260214a: VLT near-infrared observation
- EP260214b: SVOM/VT optical observation
- EP260214a: NOT optical upper limits
- EP260214a: COLIBRÍ optical upper limits
- EP260214b: OHP/T120 optical observations
- EP260214a: refined analysis of the EP-FXT observation
- EP260214b: LCO optical counterpart detection
- EP260214b: VLT/X-shooter spectroscopic redshift z = 1.208
- GRB 260211A: SVOM/VT optical counterpart
- EP260214b: COLIBRÍ optical observations
- EP260214a: SVOM/VT optical upper limits
- EP260214b: NOT optical counterpart detection
- EP260214b: Einstein Probe detection of a fast X-ray transient
- EP260214a: Global MASTER-Net observations report
- EP260214a: Einstein Probe detection of an X-ray transient
- GRB 260212A: AstroSat CZTI detection
- GRB 260212A: Fermi GBM Observation
- EP260213a: Liverpool Telescope optical upper limits
- EP260213a: Global MASTER-Net observations report
- EP260213a: COLIBRÍ optical upper limits
- GRB 260212A: GECAM-B observation
- 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
- EP260213a: refined analysis of the EP-FXT observation
- EP260213a: Einstein Probe detection of a fast X-ray transient
- EP/WXT 01709258378: NOT optical upper limits
- GRB 260212A: SVOM/GRM observation of a long burst
- GRB 260213B: Fermi GBM Final Localization
- GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
- GRB 260211A - SVOM/ECLAIRs refined analysis
- GRB 260204A: SVOM/ECLAIRs refined analysis
- GRB 260213A: Fermi GBM Final Localization
- GRB 260211A: EP-FXT follow-up observation
- GRB 260211A: SVOM/VT optical observation
- GRB 260212A: Glowbug gamma-ray detection
- GRB 260211A: GOTO optical upper limit
- Fermi GRB 260212A: Global MASTER-Net observations report
- GRB 260212A: Fermi GBM Final Real-time Localization
- GRB 260211A: LAST optical upper limit
- GRB 260210A: SVOM/GRM observation
- Fermi GBM Sub-Threshold Detection of GRB 260211A
- Konus-Wind detection of GRB 260207B
- GRB 260128B: SVOM/ECLAIRs refined analysis
- GRID detection of GRB 260207B