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.
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"
28688 results found.
- GRB 250610B: GOTO optical upper limit
- EP250610a: Global MASTER-Net observations report
- GRB 250610B : SVOM/GWAC-F60A and F50 observations
- EP250610a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250605A: Swift-BAT refined analysis
- EP250610a: SVOM/VT optical upper limit
- EP250610a: REM optical/NIR observations
- GRB 250609A: Fermi GBM Observation
- EP250610a: COLIBRÍ optical upper limit
- GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250605A: Swift/UVOT Upper Limits
- GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
- GRB 250527C: CrAO Optical Upper Limit
- GRB 250607A: SVOM/GRM observation of a long burst
- EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
- EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
- GRB 250605A: SVOM/VT optical upper limit
- Fermi GRB 250606A: Global MASTER-Net observations report
- GRB 250602A: GECAM detection
- GRB 250605A: LT optical observations
- Konus-Wind detection of GRB 250601A
- IPN triangulation of GRB 250404B
- IPN triangulation of GRB 250529A
- GRB 250601A: PRIME H band upper limit.
- GRB 250530A: SVOM/GRM analysis
- GRB 250601A: PRIME J band upper limit.
- 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 position and confirmation of GRB nature
- 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
- Fermi GRB 250601A: 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
- EP#01709177494: SVOM/VT optical observations
- Fermi GRB 250531A: Global MASTER-Net observations report
- GRB 250530C: BOOTES-7 optical upper limit
- GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
- GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
- Swift GRB 250530C: Global MASTER-Net observations report
- GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
- GRB 250530A: EP-FXT counterpart detection
- GRB 250530A: SVOM/VT optical upper limit
- GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
- GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
- GRB 250527D: CALET Gamma-Ray Burst Monitor detection
- GRB 250527C: Swift/UVOT Upper Limits
- EP J1350.0-8622: EP-FXT follow-up observation
- EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
- 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
- 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
- EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
- 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
- EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
- GRB 250521A: GRBAlpha detection
- GRB 250520A: GRBAlpha detection
- 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 250521D: SVOM/VT optical observations
- EP#01709176612: Swift-XRT counterpart detection of flaring star
- Fermi GRB 250521D: Global MASTER-Net observations report
- GRB 250521D: DDOTI Optical Upper Limit
- 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 250521A: DDOTI Optical Upper Limit
- Konus-Wind detection of GRB 250520A (short/hard)
- GRB 250520A: VLT/FORS2 Optical Observation
- GRB 250502A: Tautenburg observations
- GRB 250520A: Swift/UVOT Upper Limits
- Konus-Wind detection of GRB 250516B