GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"32572 results found.
- GRB 260208A: Fermi-LAT detection
- GRB 260207B: GECAM-B observation
- GRB 260208A: Swift ToO observations
- GRB 260208A: Fermi GBM Classification Correction
- GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
- GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
- Fermi GRB 260208A: Global MASTER-Net observations report
- GRB 260207A : MASTER optical counterpart discovery
- GRB 260131A/B: Mondy and Terskol optical observations
- Fermi GRB 260207B: Global MASTER-Net observations report
- GRB 260206A: Swift-XRT observations
- EP260131a: VLA detection
- GRB 260206A: Tiled Swift observations
- GRB 260204A: SVOM/VT confirms fading of the optical afterglow
- GRB 260204A: Swift-XRT observations
- GRB 260204A: LCO optical afterglow detection
- GRB 260204A: SVOM/VT optical candidate
- GRB 260204A : MASTER Global robotic net optical observations
- Fermi GBM Sub-Threshold Detection of GRB 260204A
- GRB 260204A: GOTO optical upper limit
- GRB 260204A: LCO optical upper limits
- EP260110a: Late GTC/EMIR near-infrared observations
- GRB 260121A: 239Alferov CubeSat detection
- 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: FTW optical and NIR observations
- 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 260130A: GECAM-B observation of a short burst
- 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 260127B: GECAM-B observation of a short burst
- GRB 260127A: GECAM-B observation
- GRB 260131A: NOT spectroscopic redshift z = 1.434
- EP260131a: Liverpool Telescope optical upper limits
- EP260131a: COLIBRÍ further observations
- Konus-Wind detection of GRB 260128A / EP260128a
- GRB 260131A: Insight-HXMT/HE detection
- Konus-Wind detection of GRB 260131A/B
- EP260131a: SVOM/VT optical observation
- EP260131a: Xinglong optical upper limit
- GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
- GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
- GRB 260131A/B: Fermi GBM Observation
- EP260131a: COLIBRÍ observations of slow optical fading
- EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
- EP260131a: NOT early detection of the counterpart in "rapid response mode"
- EP260131a: COLIBRÍ optical observations of the counterpart
- GRB 260127B: AstroSat CZTI detection
- EP260128a / GRB 260128A: COLIBRÍ optical upper limit
- Fermi GRB 260130A: Global MASTER-Net observations report
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- Fermi GRB 260129A: Global MASTER-Net observations report
- 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
- GRB 260127A: Swift-BAT refined analysis
- IPN triangulation of GRB 260127B (short)
- GRB 260127B: Swift-XRT observations
- GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
- GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
- 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: Global MASTER-Net observations report
- Fermi GRB 260127A: Global MASTER-Net observations report
- IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
- GRB 260127A: Fermi GBM Observation
- IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260127A: COLIBRÍ optical observations
- GRB 260127A: NOT optical observations
- GRB 260127B: Swift ToO observations
- EP260126a: Seimei/TriCCS optical upper limit
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127B: GOTO candidate optical counterpart
- GRB 260127A: SVOM/C-GFT optical observations
- Fermi GRB 260127B: Global MASTER-Net observations report
- Swift GRB 260127A: Global MASTER-Net observations report
- GRB 260127A: LCO optical afterglow discovery
- GRB 260125A: Swift-XRT observations
- EP260126a: EP-FXT follow-up observation
- 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
- Fermi-LAT Gamma-ray Observations of IceCube-260125A
- GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
- Konus-Wind detection of GRB 260120B
- GRB 251222A: SVOM/ECLAIRs refined analysis