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"27550 results found.
- Konus-Wind detection of GRB 260121A
- GRB 260131A/B: OHP/T193 optical observations
- GRB 260131A: KAIT optical observations
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
- GRID detection of GRB 260131A/B
- GRB 260131A/B: GTC/OSIRIS+ redshift confimation
- GRB 260130A: Insight-HXMT/HE detection
- GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
- GRB 260131A/B: EP/FXT X-ray afterglow detection
- GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
- GRB 260127B: Insight-HXMT/HE detection
- GRB 260131A: NOT spectroscopic redshift z = 1.434
- Konus-Wind detection of GRB 260128A / EP260128a
- GRB 260131A: Insight-HXMT/HE detection
- Konus-Wind detection of GRB 260131A/B
- EP260131a: Xinglong optical upper limit
- GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
- EP260131a: COLIBRÍ observations of slow optical fading
- EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
- EP260131a: NOT early detection of the counterpart in "rapid response mode"
- GRB 260131B: MAXI/GSC detection
- GRB 260131A: Fermi GBM Final Real-time Localization
- EP260131a: Las Cumbres detection of an optical counterpart
- GRB 260127B: AstroSat CZTI detection
- GRB 260130A: Fermi GBM Detection
- EP260131a: Einstein Probe detection of an X-ray transient
- GRB 260127B: Fermi GBM Detection
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- GRB 260130A: Fermi GBM Final Real-time Localization
- EP260128a: J band upper limit by SYSU 80cm infrared telescope
- GRB 260129B: Fermi GBM Final Localization
- GRB 260128B: SVOM detection of a burst through offline search
- GRB 260129A: Fermi GBM Final Localization
- IPN triangulation of GRB 260127B (short)
- GRB 260127B: Swift-XRT observations
- GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
- EP260128a: NOT optical counterpart candidate
- EP260128a: Liverpool Telescope optical observations and possible counterpart
- EP260126a: SVOM/VT optical upperlimit
- EP260128a: Einstein Probe detection of an X-ray transient
- GRB 260127A: Fermi GBM Observation
- GRB 260127B: Swift ToO observations
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: Swift-XRT refined Analysis
- GRB 260127A: SVOM/C-GFT optical observations
- GRB 260127A: Enhanced Swift-XRT position
- GRB 260127B: Fermi GBM Final Real-time Localization
- GRB 260127A: Prompt enhanced Swift-XRT position
- GRB 260127A: LCO optical afterglow discovery
- GRB 260127A: Swift detection of a burst
- GRB 260127A: Fermi GBM Final Real-time Localization
- GRB 260125A: Swift-XRT observations
- EP260126a: EP-FXT follow-up observation
- EP260126a: Liverpool Telescope optical upper limits
- EP260126a: Further NOT optical upper limits
- EP260126a: Einstein Probe detection of a fast X-ray transient
- Konus-Wind detection of GRB 260120B
- GRB 260125A: Swift ToO observations
- GRB 260125A: GOTO candidate optical counterpart
- IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260125B: Fermi GBM Final Real-time Localization
- GRB 260125A: Fermi GBM Final Real-time Localization
- GRB 260114A: SVOM/VT optical upper limits
- GRB 260120A: AstroSat CZTI detection
- GRB 260120B: AstroSat CZTI detection
- GRB 260114A: Insight-HXMT/HE detection
- GRB 260122B: Swift detection of a burst
- GRB 260122A: Fermi GBM Final Real-time Localization
- EP260119a: Xinglong optical upper limit
- GRB 260120B: Swift-XRT refined Analysis
- GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
- GRB 260120B: Fermi GBM Observation
- 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
- GRB 260120C: Fermi GBM Final Real-time Localization
- GRB 260101A: 239Alferov CubeSat detection
- GRB 260120B: Swift detection of a burst
- GRB 260120B: Fermi GBM Final Real-time Localization
- EP260119A: Mondy I-Band Observations
- GRB 260114A: Swift/UVOT Upper Limits
- EP260119a: Liverpool Telescope optical follow-up observations
- Trigger 1442421: Swift detection of HMXB 1A 1118-61
- EP260119a: KAIT optical observations
- GRB 260120A: Fermi GBM Final Real-time Localization
- EP260119a: update of EP-FXT follow-up observation
- EP260116a: COLIBRÍ detection of a fading optical source
- GRB 260117A: Swift-XRT afterglow detection
- GRB 260115A: AstroSat CZTI detection
- EP260119a: LCO optical observations
- GRB 260117A: ZTSh optical upper limit
- EP260119a: preliminary result from the EP-FXT observation
- GRB 260110A: SVOM detection of a burst through offline search
- 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/VT optical candidate