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"22854 results found.
- GRB 260208A: Mondy optical observations
- GRB 260208A: 1.3m DFOT optical detection
- GRB 260208A: COLIBRÍ optical observations
- GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
- GRB 260208A: SVOM/VT optical observation
- GRB 260208B: SVOM/GRM observation of a bright burst
- GRB 260131A/B: Mondy and Terskol optical observations
- GRB 260206A: Swift-XRT observations
- EP260131a: VLA detection
- GRB 260204A: Swift-XRT observations
- GRB 260204A: SVOM/VT optical candidate
- GRB 260204A : MASTER Global robotic net optical observations
- GRB 260204A: LCO optical upper limits
- EP260110a: Late GTC/EMIR near-infrared observations
- GRB 260131A: KAIT optical observations
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
- GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
- EP260131a: Liverpool Telescope optical upper limits
- EP260131a: COLIBRÍ further observations
- EP260131a: SVOM/VT optical observation
- EP260131a: Xinglong optical upper limit
- GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
- EP260131a: COLIBRÍ observations of slow optical fading
- EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260131a: NOT early detection of the counterpart in "rapid response mode"
- EP260131a: COLIBRÍ optical observations of the counterpart
- EP260131a: Einstein Probe detection of an X-ray transient
- EP260128a / GRB 260128A: COLIBRÍ optical upper limit
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- GRB 260128B: LCO optical upper limits
- GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
- EP260128a: J band upper limit by SYSU 80cm infrared telescope
- IPN triangulation of GRB 260121A
- IPN triangulation of GRB 260127B (short)
- GRB 260127B: Swift-XRT observations
- GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
- EP260128a: NOT optical counterpart candidate
- EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260128a: Liverpool Telescope optical observations and possible counterpart
- EP260128a: LCO optical upper limits
- EP260126a: SVOM/VT optical upperlimit
- 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