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 250530A: SVOM/VT optical upper limit
- Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
- GRB 250530B: Fermi GBM Final Real-time Localization
- GRB 250530A: Swift-XRT counterpart detection
- GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
- GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
- GRB 250530A: SVOM detection of a burst
- GRB 250527D: CALET Gamma-Ray Burst Monitor detection
- GRB 250527C: Swift/UVOT Upper Limits
- GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
- EP J1350.0-8622: EP-FXT follow-up observation
- GRB 250529B: Fermi GBM Final Real-time Localization
- GRB 250527B: Swift-XRT observations
- EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
- The EP-WXT trigger 01709177124 is likely a flaring star
- GRB 250529A: Fermi GBM Final Real-time Localization
- GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
- GRB 250520A: Swift-BAT refined analysis
- GRB 250527C: Swift ToO observations
- GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
- EP250526a: SVOM/VT optical upper limit
- GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
- GRB 250527B: Tiled Swift observations
- GRB 250520A: Gemini-South optical afterglow detection
- Fermi trigger No 770058372: Global MASTER-Net observations report
- Fermi trigger No 770047117: Global MASTER-Net observations report
- GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
- GRB 250527A: Fermi GBM Final Localization
- EP250526a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250314A: CIDER NB1008 upper limit
- EP250526a: COLIBRÍ optical upper limits
- EP250526a: Global MASTER-Net observations report
- EP250526a: Einstein Probe detection of a fast X-ray transient
- EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
- EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
- EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
- GRB 250520A: 3 GHz MeerKAT Detection
- GRB 250520A: 10 GHz VLA Afterglow Confirmation
- Fermi GRB 250523A: Global MASTER-Net observations report
- Fermi trigger No 769611916: Global MASTER-Net observations report
- EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
- GRB 250521A: GRBAlpha detection
- GRB 250520A: GRBAlpha detection
- GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
- GRB 250523A: Fermi GBM Final Real-time Localization
- The EP-WXT trigger 01709176712 is likely a flaring star
- GRB 250521B: SVOM/VT optical upper limit
- The EP-WXT trigger 01709176612: SVOM/VT optical observations
- The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
- Fermi GRB 250522B: Global MASTER-Net observations report
- GRB 250521B: EP-FXT follow-up observation and afterglow candidates
- GRB 250522B: Fermi GBM Final Localization
- GRB 250521D: SVOM/VT optical observations
- GRB 250522A: Fermi GBM Final Real-time Localization
- EP#01709176612: Swift-XRT counterpart detection of flaring star
- Fermi GRB 250521D: Global MASTER-Net observations report
- Fermi trigger No 769533898: Global MASTER-Net observations report
- Fermi trigger No 769499303: Global MASTER-Net observations report
- GRB 250521D: DDOTI Optical Upper Limit
- The EP-WXT trigger 01709176612 is likely a flaring star
- GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
- GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250521D: LAST tentative optical counterpart candidate
- GRB 250520A: CALET Gamma-Ray Burst Monitor detection
- GRB 250520A: 10 GHz VLA radio source
- GRB 250521B: Swift ToO observations
- GRB 250521D: Fermi GBM Final Real-time Localization
- GRB 250521C: Fermi GBM Final Localization
- GRB 250521A: DDOTI Optical Upper Limit
- GRB 250521B: SVOM detection of a burst through offline search
- Konus-Wind detection of GRB 250520A (short/hard)
- GRB 250520A: VLT/FORS2 Optical Observation
- GRB 250502A: Tautenburg observations
- GRB 250520A: Swift/UVOT Upper Limits
- GRB 250521A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 250516B
- IPN triangulation of GRB 250516B
- GRB 250520A: J-band observations with WINTER
- GRB 250520A: Gemini-South optical observations
- GRB 250520A: Swift-XRT refined Analysis
- GRB 250520A: REM optical/NIR early observations
- GRB 250520B: Fermi GBM Final Real-time Localization
- GRB 250520A：SVOM/VT optical candidate
- GRB 250520A: COLIBRÍ optical upper limit
- GRB 250520A: DDOTI Optical Upper Limit
- GRB 250520A: AstroSat CZTI detection of a short burst
- GRB 250516B: GRBAlpha detection
- GRB 250520A: SVOM/GRM observation
- GRB 250520A: Enhanced Swift-XRT position
- GRB 250520A: GOTO optical upper limit
- GRB 250520A: Prompt enhanced Swift-XRT position
- GRB 250520A: Swift detection of a burst
- Swift GRB 250520A: Global MASTER-Net observations report
- GRB 250516B: Insight-HXMT detection
- EP250427a/GRB250427A: VLA Detection of Radio Counterpart
- GRB 250516A: Swift-BAT refined analysis
- GRB 250516A: COLIBRÍ optical upper limit
- Konus-Wind detection of GRB 250516A
- GRB 250516B: NuSTAR Detection of the Prompt Emission
- EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317