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"28077 results found.
- GRB 250527C: Swift/UVOT Upper Limits
- 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
- GRB 250529A: Fermi GBM Final Real-time Localization
- GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
- GRB 250527C: Swift ToO observations
- GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250527B: Tiled Swift observations
- GRB 250520A: Gemini-South optical afterglow detection
- GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
- GRB 250527A: Fermi GBM Final Localization
- 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
- GRB 250520A: 3 GHz MeerKAT Detection
- GRB 250520A: 10 GHz VLA Afterglow Confirmation
- GRB 250521A: GRBAlpha detection
- GRB 250520A: GRBAlpha detection
- GRB 250523A: Fermi GBM Final Real-time Localization
- GRB 250521B: SVOM/VT optical upper limit
- The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
- GRB 250521B: EP-FXT follow-up observation and afterglow candidates
- GRB 250522B: Fermi GBM Final Localization
- GRB 250522A: Fermi GBM Final Real-time Localization
- EP#01709176612: Swift-XRT counterpart detection of flaring star
- GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
- GRB 250521D: LAST tentative optical counterpart candidate
- GRB 250520A: CALET Gamma-Ray Burst Monitor detection
- GRB 250521B: Swift ToO observations
- GRB 250521D: Fermi GBM Final Real-time Localization
- GRB 250521C: Fermi GBM Final Localization
- 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 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: AstroSat CZTI detection of a short burst
- GRB 250516B: GRBAlpha detection
- 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
- GRB 250516B: Insight-HXMT detection
- EP250427a/GRB250427A: VLA Detection of Radio Counterpart
- 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
- GRB 250515A: Swift-XRT observations
- GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
- GRB 250515A: 1.6m Mephisto optical detection
- GRB 250516A: AstroSat CZTI detection
- GRB 250516A: Swift-XRT refined Analysis
- GRB 250516A: Swift/UVOT Detection
- GRB 250515A: Swift ToO observations
- GRB 250516B: GECAM-B detection of a bright long burst
- GRB 250516A: Enhanced Swift-XRT position
- GRB 250516A: Swift detection of a burst
- GRB 250516A: Fermi GBM Final Real-time Localization
- GRB 250515A: Fermi GBM Final Localization
- GRB 250424A: COLIBRÍ detection of the associated supernova
- Konus-Wind detection of GRB 250512B / EP250512a
- GRB 250502A: TESS observations
- GRB 250511A: GECAM-A detection of a short burst
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
- Konus-Wind detection of GRB 250506A
- EP250512a/GRB 250512B: REM optical/NIR observations
- GRB 250507B: AstroSat CZTI detection
- GRB 250507B: GRBAlpha detection
- GRB 250506A: GRBAlpha detection
- GRB 250512B: SVOM detection of a burst
- EP250512a: Einstein Probe detection of an X-ray transient
- GRB 250512A: Fermi GBM Final Real-time Localization
- EP250511a: REM optical/NIR observations
- EP250511a: BOOTES-5 optical upper limit
- EP250511a: Einstein Probe detection of an X-ray transient
- EP250508a: Gemini NIR upper limits
- GRB 250510C: Fermi GBM Final Real-time Localization
- GRB 250510A: Swift-XRT observations
- GRB 250510A: follow-up observation with EP-FXT
- GRB 250510B: Fermi GBM Final Localization
- GRB 250509A: Swift-XRT refined Analysis
- GRB 250510A: SVOM possible detection of a burst
- GRB 250507A: J-band observations with WINTER
- GRB 250509A: Enhanced Swift-XRT position
- GRB 250509A: Prompt enhanced Swift-XRT position
- GRB 250509A: Swift detection of a burst
- GRB 250509A: Fermi GBM Final Real-time Localization
- GRB 250506A: NOT optical upper limits