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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
3035 results found.
- EP250428b: refined analysis of the EP-FXT follow-up observation
- GRB 250427A: Swift/UVOT Detection
- EP250427a: EP-FXT follow-up observations
- GRB 250427A: Swift-XRT refined Analysis
- GRB 250424A: Swift-XRT refined Analysis
- SVOM/sb25042207: XRT observations
- EP250421a: Swift/XRT counterpart detection
- GRB 250419A: Swift-XRT refined Analysis
- EP250416a: Swift/XRT counterpart fading
- EP20250416a: Swift/XRT counterpart detection
- SVOM/sb25041603 is not a GRB
- IceCube-250406A: Swift-XRT observations
- EP250407a: Swift-XRT observations
- GRB 250407A: Swift-XRT afterglow detection
- GRB 250331D: Swift-XRT afterglow detection
- EP250402a: EP-FXT follow-up observations
- GRB 250403A: Swift-XRT observations
- GRB 250402A: Swift-XRT observations
- GRB 250402A: refined SVOM/MXT data analysis
- GRB 250329B: Swift/UVOT Upper Limit
- GRB 250327A: Swift/UVOT Upper Limits
- GRB 250331D: Swift-XRT observations
- GRB 250331C: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250328A: Swift-XRT refined Analysis
- GRB 250331C: Prompt enhanced Swift-XRT position
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250330A: Prompt Swift-XRT position
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250327A: SVOM/VT upper limits on the XRT position
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327A: Swift-XRT refined Analysis
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- GRB 250321B: Swift-XRT observations
- GRB 250322A: Swift-XRT refined Analysis
- FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
- EP250321a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250321A: Swift-XRT refined Analysis
- EP250321a: Swift-XRT detection of an X-ray source
- GRB 250321A: Swift-XRT localisation
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Swift-XRT observations
- GRB 250316A: Swift/UVOT Upper Limits
- GRB 250316A: Swift-XRT afterglow detection
- GRB 250316A: Swift-XRT observations
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250314A: SVOM/VT upper limit
- GRB 250313A: Swift-XRT observations
- EP250302a: Chandra X-ray Detection
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250311A: Swift-XRT observations
- GRB 250309B: Swift-XRT refined Analysis
- EP250308a: Einstein Probe detection of an X-ray transient
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250304a: Swift-XRT detection of a fading X-ray source
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: Swift-XRT observations of a fading X-ray source
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250225a: EP-FXT follow-up observation
- GRB 250221A: EP-FXT detection of the X-ray afterglow
- LIGO/Virgo S250223dk: Swift XRT observations, 7 X-ray sources
- EP250220a: EP-FXT follow-up observations
- GRB 250221A: Swift-XRT refined Analysis
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: Swift-XRT observations
- GRB 250217C: Swift-XRT observations
- GRB 250213A: Swift-XRT observations
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: Swift-XRT refined Analysis
- EP250207B: Chandra localization of the X-ray counterpart
- GRB 250210A: AstroSat CZTI detection
- GRB 250206A: Swift-XRT observations
- GRB 250207B: Swift-XRT observations
- GRB 250207A: Swift-XRT refined Analysis
- GRB 250205A: Swift/XRT detection
- GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
- GRB 250129A: Swift-XRT refined Analysis
- GRB 250128B: Swift-XRT refined Analysis
- GRB 250127A: Swift-XRT observations
- GRB 250127A: EP-FXT afterglow detection
- LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
- GRB 250114B: Swift-XRT afterglow detection
- GRB 250114B: Swift-XRT observations
- GRB 250114A: Swift-XRT refined Analysis
- GRB 250106A: Swift-XRT afterglow detection
- GRB 250108A: Swift/XRT afterglow fading
- EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
- EP250108a: EP-FXT follow-up observation
- GRB 250108B: Swift-XRT refined Analysis
- GRB 250108A: Swift-XRT afterglow detection
- GRB 250103A: Swift-XRT afterglow detection
- GRB 250106A: Swift-XRT observations
- GRB 250103B: Swift-XRT refined Analysis
- GRB 250103A: Swift-XRT observations
- GRB 250101A: Swift-XRT refined Analysis
- GRB 241229A: EP-FXT X-ray afterglow confirmation
- GRB 241229A: Swift-XRT observations