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"3400 results found.
- 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
- GRB 241229A: EP-FXT afterglow candidates
- GRB 241228B: Swift-XRT afterglow detection
- GRB 241229B: Swift-XRT refined Analysis
- GRB 241228A: Swift-XRT refined Analysis
- GRB 241223A: Swift-XRT observations
- EP 241217a: NIR detection with P200/WIRC
- GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
- GRB 241218A: Swift-XRT refined Analysis
- GRB 241217A: Swift-XRT afterglow detection
- EP241217a: Swift-XRT Detection
- GRB 241212A: Swift-XRT observations
- GRB 241213B: Swift-XRT observations
- GRB 241213A: Swift-XRT refined Analysis
- EP241213a: EP detection of An X-ray Transient
- GRB 241209A: Chandra X-ray Detection
- GRB 241209B: Swift-XRT afterglow detection
- GRB 241209A: Swift-XRT refined Analysis
- EP241208a: EP-FXT follow-up observations
- GRB 241209D: Swift-XRT refined Analysis
- GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
- AT2024adec: X-ray Upper Limits from EP-FXT Observation
- EP241201a: EP-FXT follow-up observations
- Fermi trigger No 754701230: Global MASTER-Net observations report
- Swift-XRT observations of IceCube -241127A
- GRB 241128A: Swift-XRT refined Analysis
- GRB 241128A: Swift-XRT afterglow detection
- GRB 241127A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S241125n: Swift-UVOT Upper Limits
- LIGO/Virgo/KAGRA S241125n: EP-FXT follow-up observations
- LIGO/Virgo S241125n: Swift XRT observations, 5 X-ray sources
- GRB 241115A: Swift-XRT afterglow detection
- GRB 241113B: Swift-XRT observations
- GRB 241113A: Swift-XRT refined Analysis
- GRB 241112B: Swift-XRT afterglow detection
- GRB 241108A: Swift-XRT observations