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 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
- GRB 250602A: GECAM detection
- Fermi trigger No 770867684: Global MASTER-Net observations report
- The EP-WXT trigger 01709177873 is likely a flaring star
- GRB 250605A: LT optical observations
- GRB 250605A: Swift detection of a burst
- Swift GRB250605.79: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250601A
- IPN triangulation of GRB 250404B
- IPN triangulation of GRB 250529A
- The EP-WXT trigger 01709177837 is likely a flaring star
- Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
- GRB 250601A: PRIME H band upper limit.
- GRB 250530A: SVOM/GRM analysis
- GRB 250601A: PRIME J band upper limit.
- Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
- GRB 250601A: VLT/FORS2 Optical Observation
- GRB 250601A: Fermi GBM Observation
- GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
- GRB 250603A: Swift/UVOT Upper Limits
- GRB 250603A: Swift-XRT refined Analysis
- Fermi trigger No 770638414: Global MASTER-Net observations report
- GRB 250603A: Enhanced Swift-XRT position
- GRB 250603A: Swift-XRT position and confirmation of GRB nature
- Swift GRB250603.05: Global MASTER-Net observations report
- GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
- GRB 250602A: Fermi GBM Observation
- GRB 250602A: Fermi-LAT detection
- GRB 250602A: DDOTI Optical Upper Limit
- GRB 250530C: Swift-BAT refined analysis
- GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
- GRB 250601A: EP-FXT follow-up observation and afterglow candidates
- GRB 250601A: Swift/XRT candidate afterglow
- GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
- GRB 250601A: Swift-XRT observations
- Fermi GRB 250601A: Global MASTER-Net observations report
- GRB 250602A: Fermi GBM Final Real-time Localization
- Fermi trigger No 770470765: Global MASTER-Net observations report
- GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
- GRB 250601A: Swift ToO observations
- GRB 250530A: VLT/HAWK-I NIR counterpart fading
- GRB 250521C/AT2025mgj: FTW optical and NIR observations
- GRB 250601A: Fermi GBM Final Real-time Localization
- EP#01709177494: SVOM/VT optical observations
- Fermi GRB 250531A: Global MASTER-Net observations report
- GRB 250531A: Fermi GBM Final Real-time Localization
- EP#01709177494: Swift-XRT counterpart detection of known source
- GRB 250530C: BOOTES-7 optical upper limit
- GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
- GRB 250530C: Swift-XRT refined Analysis
- GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
- Swift GRB 250530C: Global MASTER-Net observations report
- GRB 250530C: Enhanced Swift-XRT position