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.
- GRB 251011B: Swift-XRT refined Analysis
- GRB 251011B : MASTER optical observations
- GRB 251006B/EP251006a: EP-FXT afterglow detection
- GRB 251007A: Swift-XRT refined Analysis
- GRB 251007B: Swift-XRT refined Analysis
- GRB 251006B/EP251006a: EP-FXT follow-up observation
- GRB 251005C: Swift-XRT refined Analysis
- GRB 251002A: Swift/UVOT detection
- GRB 251003A: Swift-XRT refined Analysis
- GRB 251002A: Swift-XRT afterglow detection
- GRB 251001B: Swift-XRT refined Analysis
- GRB 250925A: Swift-XRT refined Analysis
- GRB 250925A: Swift/UVOT Upper Limits
- GRB 250924A: Swift-XRT refined Analysis
- GRB 250920C: Swift-XRT refined Analysis
- GRB 250920B: Swift-XRT refined Analysis
- GRB 250919A: Swift-XRT afterglow detection
- GRB 250919A: Fermi-LAT detection
- GRB 250917B: VLT/HAWK-I near-infrared observations
- GRB 250916A: Swift-XRT observations
- EP250916a: EP-FXT follow-up observation
- GRB 250917B: Swift-XRT observations
- GRB 250912A: Swift-XRT observations
- GRB 250911A: Swift-XRT refined Analysis
- EP250911a: Swift-XRT observations
- GRB 250911A: Swift/UVOT Detection
- GRB 250910A / EP250910a: Swift-XRT afterglow detection
- GRB 250702B: Late time Chandra observations
- EP#01709240653: Swift-XRT observations
- GRB 250903A: Swift-XRT afterglow detection
- EP250905b: EP-FXT follow-up observation
- GRB 250905A: Swift-XRT refined Analysis
- GRB 250903A: Swift/UVOT detection
- GRB 250904A: Swift-XRT refined Analysis
- GRB 250903A: Swift-XRT observations
- EP250903a: Swift-XRT observations
- EP#01709201209: Swift-XRT observations
- GRB 250901A: Swift/UVOT Upper Limit
- GRB 250830B: Swift-XRT afterglow detection
- GRB 250901A: EP-FXT follow-up observation
- GRB 250901A: Swift-XRT afterglow detection
- EP250901a: Swift-XRT observations
- EP250831a: EP-FXT follow-up observation
- EP250831a: Swift-XRT observations
- GRB 250831A: Swift-XRT counterpart detection
- GRB 250830B: Swift-XRT observations
- EP250827a: Swift/UVOT Detection
- EP250827a: Swift-XRT counterpart detection
- LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
- GRB 250823A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
- EP250821a: Swift/XRT counterpart fading
- GRB 250821A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
- EP250821a: Swift XRT and UVOT counterpart detection
- GRB 250821A: Prompt enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
- GRB 250813B: Swift/UVOT Upper Limit
- GRB 250818B: Swift/UVOT Detection
- GRB 250818A: Swift-XRT refined Analysis
- GRB 250818B: EP-FXT counterpart detection
- GRB 250818B: Swift-XRT afterglow detection
- sb25081602: Swift-XRT observations
- LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
- GRB 250814A: P200/WIRC observations of the afterglow candidate
- GRB 250814A: Swift-XRT refined Analysis
- GRB 250814A: Possible afterglow candidate from P200/WIRC
- GRB 250813B: EP-FXT counterpart detection
- GRB 250813B: Swift-XRT afterglow detection
- GRB 250812A: Swift/UVOT Detection
- EP250812a: Swift-XRT counterpart detection
- GRB 250812A: Swift-XRT afterglow detection
- GRB 250809A: Swift-XRT refined Analysis
- GRB 250702B: Chandra X-ray Detection
- GRB 250808A: Swift-XRT candidate counterpart detection
- GRB 250807A: Swift-XRT refined Analysis
- GRB 250807B: Swift-XRT refined Analysis
- GRB 250806A: EP-FXT observation
- EP#01709198415/EP250806a: Swift-XRT observations
- EP250802a: EP-FXT follow-up observation
- GRB 250806A: Swift-XRT counterpart detection
- GRB 250805A: Swift-XRT refined Analysis
- GRB 250804B: Swift-XRT observations
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- GRB 250728A: Swift-XRT observations
- GRB 250727A: Swift-XRT observations
- GRB 250725A: Swift-XRT refined Analysis
- SVOM J195836+32283 is not a real source
- SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
- GRB 250721A: Swift-XRT observations
- Fermi trigger No 774730635: Global MASTER-Net observations report
- GRB 250717B: Swift-XRT observations
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250713A: Swift-XRT observations
- GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
- IceCube-250706A: EP-FXT follow-up observations
- GRB 250706B/C: Fermi-LAT detection
- GRB 250706B: Swift/UVOT Detection
- EP250702a/ GRB 250702B: NuSTAR X-ray Observations