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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"22912 results found.
- EP260128a: Einstein Probe detection of an X-ray transient
- GRB 260127A: COLIBRÍ optical observations
- EP260126a: Seimei/TriCCS optical upper limit
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: SVOM/C-GFT optical observations
- GRB 260127A: Enhanced Swift-XRT position
- GRB 260127A: LCO optical afterglow discovery
- GRB 260127A: Swift detection of a burst
- GRB 260125A: Swift-XRT observations
- EP260126a: Optical upper limit with Kinder observations
- EP260126a: Liverpool Telescope optical upper limits
- EP260126a: Further NOT optical upper limits
- EP260126a: COLIBRÍ optical upper limits
- EP260126a: NOT optical observations
- EP260126a: Einstein Probe detection of a fast X-ray transient
- Konus-Wind detection of GRB 260120B
- GRB 260125A: GOTO candidate optical counterpart
- GRB 260114A: SVOM/VT optical upper limits
- GRB 260120A: AstroSat CZTI detection
- GRB 260120B: SVOM/GRM observation
- GRB 260122B: Swift detection of a burst
- EP260119a: Assy AZT-20 optical observations
- EP260119a: Mondy and SAO RAS optical upper limits
- EP260119a: Xinglong optical upper limit
- EP260116a: COLIBRÍ further observations
- GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
- EP260105a: GTC/HiPERCAM optical observations
- GRB 260120B: Swift/UVOT Detection
- GRB 260120B: COLIBRÍ optical upper limits
- GRB 260120B: Enhanced Swift-XRT position
- GRB 260120B: SVOM/C-GFT optical counterpart detection
- EP260116a: COLIBRÍ observations of a tentative optical rebrightening
- GRB 260120B: Swift detection of a burst
- EP260119A: Mondy I-Band Observations
- GRB 260114A: Swift/UVOT Upper Limits
- EP260119a: Liverpool Telescope optical follow-up observations
- GRB 251202A: further radio observations with the VLA
- EP260119a: KAIT optical observations
- EP260119a: SVOM/VT optical observation
- EP260119a: NOT optical observations
- EP260119a: SAO RAS optical observations
- EP260116a: COLIBRÍ detection of a fading optical source
- GRB 260117A: Swift-XRT afterglow detection
- EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
- EP260119a: LCO optical observations
- GRB 260117A: ZTSh optical upper limit
- EP260119a: COLIBRÍ optical counterpart candidate
- EP260119a: EP-WXT detection of a fast X-ray transient
- GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
- Swift trigger on the HMXB 1A 1118-61
- GRB 260117A: SVOM/C-GFT upper limit
- GRB 260117A: Swift-XRT observations
- EP 260116a: COLIBRÍ optical upper limit
- Swift triggered on the HMXB 1A 1118-61
- FRB 20251229A: COLIBRÍ further inspection of the updated localization
- EP260116a: Liverpool Telescope upper limits
- EP260116A: 1.3m DFOT optical upper limit
- GRB 260114A: VLT/MUSE spectroscopic observations
- GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
- EP260116a: Xinglong optical upper limit
- EP260116a: Einstein Probe detection of an X-ray transient
- GRB 260114A: VLT/HAWK-I further near-infrared upper limits
- GRB260114A: STEP/T80S optical limits
- GRB 251222A: radio detection with the VLA
- GRB 260114A: VLT/HAWK-I near-infrared upper limits
- GRB 260114A: Swift-XRT refined Analysis
- GRB 260114A: 6 GHz VLA observations
- GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
- GRB 260114A : MITSuME Akeno optical upper limits
- GRB 260114A: COLIBRÍ optical upper limits
- GRB 260114A: TNG NIR upper limit
- GRB 260114A: NOT optical observations
- GRB 260114A: SVOM/GRM observation of a short burst
- GRB 260114A: Mondy optical observations
- GRB 260114A: GMG Optical Observation
- GRB 260114A: Swift detection of a short burst
- EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
- EP260110a: NOT and GTC Optical and Near-Infrared Observations
- EP260110a: TRT optical upper limits
- Konus-Wind detection of GRB 260101A
- GRB 260111A: Swift-XRT observations
- Swift Trigger 1439093: is probably not GRB 260113A
- GRB 260111A: COLIBRÍ optical afterglow candidate
- GRB 251230A: Mondy Optical Observations
- EP260110a: SVOM/VT optical upper limits
- Swift trigger 1436759 is not an astrophysical event
- EP260110a: KAIT optical upper limit
- EP260110a: refined analysis of the EP-WXT and EP-FXT observations
- EP 260110a: COLIBRÍ optical observations
- EP260110a: SVOM/C-GFT upper limit
- EP260110a: Einstein Probe detection of an X-ray transient
- GRB 260109C: LCO optical upper limits
- GRB 260109C: Kilonova-Catcher optical upper limit
- Swift Trigger 1434591: possible GRB 260109C
- GRB 260102A: Swift-XRT afterglow detection
- GRB 260102A: AbAO optical observations
- EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
- EP260105a: FTW optical observations
- EP260104a: FTW optical observations
- GRB 260105A: SVOM/GRM observation