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 250615A: Prompt enhanced Swift-XRT position
- GRB 250615A: Swift detection of a burst
- Swift GRB 250615A: Global MASTER-Net observations report
- Fermi trigger No 771718064: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
- GRID detection of GRB 250612C
- sb25061207: Mephisto optical upper limits
- IceCube alert 141029_8144692 retraction
- Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
- GRB 250614A: Fermi GBM Final Real-time Localization
- EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
- Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
- Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
- sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- Fermi trigger No 771494087: Global MASTER-Net observations report
- sb25061218: Swift-XRT observations
- EP250612a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
- sb25061207: EP-FXT follow-up observation and afterglow candidate
- GRB 250612B: Fermi GBM Observation
- EP250612a: SVOM/VT optical candidate
- Fermi trigger No 771424081: Global MASTER-Net observations report
- EP250612a: Global MASTER-Net observations report
- GRB 250612C: Fermi GBM Observation
- sb25061218: SVOM detection of a X-ray transient
- sb25061207: Swift-XRT observations
- EP250612a/GRB 250612B: JinShan optical upper limit
- EP 250612a: AST3-3 Yaoan Optical Observation
- GRB 250612C: SVOM/GRM observation an intermedium duration burst
- sb25061207: SVOM/VT optical counterpart
- GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
- GRB 250610B: Swift-XRT refined Analysis
- GRB 250612C: Fermi GBM Final Real-time Localization
- EP250610a: Upper limit from Fermi-GBM Observations
- GRB 250612B (250612519/771424081): Fermi GBM Final Localization
- GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
- EP250612a: Einstein Probe detection of an X-ray transient
- GRB 250610B: Liverpool Telescope continued monitoring
- GRB 250610B: MISTRAL/T193 and T120 OHP further observations
- sb25061207: SVOM detection of a X-ray transient
- EP250610a: continuous follow-up observations with EP-FXT
- GRB 250610B - SVOM/ECLAIRs refined analysis
- GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
- Swift GRB250612.04: Global MASTER-Net observations report
- Fermi GBM Sub-Threshold Detection of GRB 250610B
- GRB 250610B: Swift/UVOT Detection
- EP250610A: Swift/UVOT Upper limits
- GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
- EP250610a: TNG NIR upper limit
- GRB 250610B: REM optical/NIR observations
- EP250610a: Liverpool Telescope optical upper limits
- GRB 250610B: SVOM/VT optical shallow decay
- GRB 250610B: additional Liverpool Telescope optical observations
- GRB 250610B: SVOM/GRM analysis
- GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
- GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
- Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
- GRB 250610B: Swift-XRT counterpart detection
- GRB 250610B: SVOM/VT optical counterpart
- GRB 250610B: LT detection of the optical counterpart
- GRB 250610B: OHP/T120 optical counterpart candidate
- GRB 250610C: Fermi GBM Final Real-time Localization
- GRB 250610B: GOTO optical upper limit
- EP250610a: Global MASTER-Net observations report
- GRB 250610B : SVOM/GWAC-F60A and F50 observations
- GRB 250610B: SVOM detection of a long burst
- Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
- EP250610a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250610A: Fermi GBM Final Real-time Localization
- GRB 250605A: Swift-BAT refined analysis
- EP250610a: SVOM/VT optical upper limit
- EP250610a: REM optical/NIR observations
- GRB 250609A: Fermi GBM Observation
- GRBAlpha reentry on June 9, 2025
- EP250610a: Swift-XRT counterpart detection
- EP250610a: COLIBRÍ optical upper limit
- EP250610a: Einstein Probe detection of an X-ray transient
- Fermi trigger No 771072240: Global MASTER-Net observations report
- GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250605A: Swift/UVOT Upper Limits
- The EP-WXT trigger 01709178283 is likely a flaring star
- GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
- GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
- GRB 250527C: CrAO Optical Upper Limit
- GRB 250609A: Fermi GBM Final Real-time Localization
- GRB 250607A: SVOM/GRM observation of a long burst
- EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
- The EP-WXT trigger 01709178244 is likely a flaring star
- GRB 250607A: Fermi GBM Final Localization
- EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
- The EP-WXT trigger 01709178069 is likely a flaring star
- GRB 250605A: SVOM/VT optical upper limit
- GRB 250605A: Swift-XRT refined Analysis
- EP/WXT 01709177873: GOTO observations confirm stellar variability
- GRB 250605A: Enhanced Swift-XRT position
- Fermi GRB 250606A: Global MASTER-Net observations report
- GRB 250606A: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
- Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB