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"32541 results found.
- GRB 260730B: Glowbug gamma-ray detection
- GRB 260805B: Glowbug gamma-ray detection
- Fermi GRB 260805A: Global MASTER-Net observations report
- GRB 260804A: Glowbug gamma-ray detection
- GRB 260730B: CALET Gamma-Ray Burst Monitor detection
- GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
- GRB 260708A: LCO further optical observations show supernova features
- Fermi GRB 260802B: Global MASTER-Net observations report
- GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
- GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
- GRB 260802A: SVOM/VT optical upper limits from VHF data
- GRB 260802A: LCO optical upper limits
- GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
- GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
- Fermi-LAT Gamma-ray Observations of IceCube-260722A
- GRB 260730B: AstroSat CZTI detection
- EP260731a: COLIBRÍ optical upper limit
- EP260731a: NOT optical upper limit
- GRB 260730B: NuSTAR detection of prompt emission
- GRB 260727A: SVOM/ECLAIRs refined analysis
- GRB 260726A: SVOM/ECLAIRs refined analysis
- EP260728a: COLIBRÍ optical upper limit
- EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
- The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
- EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
- EP260727a: SAO RAS optical observations
- GRB 260727A: AbAO and SAO RAS optical observations
- EP260728a: EP-FXT follow-up observation
- GRB 260726A: EP-FXT follow-up observations
- GRB 260727A: SVOM/GRM observation
- GRB 260726A: Fermi GBM Observation
- EP260727a: 1.5m OSN optical counterpart detection
- EP260727a:refined analysis of the EP-WXT and EP-FXT observation
- EP260727a: OHP/T193 optical observations
- Konus-Wind detection of GRB 260727A
- GRB 260726A: Liverpool Telescope optical observations
- GRB 260727A: Liverpool Telescope optical upper limits
- EP260727a: Liverpool Telescope confirmation of optical counterpart
- EP260727a: NUTTELA-TAO Early Optical Limits
- GRB 260727A: EP/FXT follow-up observations
- EP260727a: Einstein Probe detection of an X-ray transient
- GRB 260727A: Glowbug gamma-ray detection
- GRB 260726A: J-band upper limit with WINTER
- GRB 260727A: J-band upper limit with WINTER
- GRB 260726A: SVOM/VT optical candidate
- GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
- GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
- EP260723a: SVOM/ECLAIRs Upper Limit
- GRB 260727A: GOTO early optical upper limit
- GRB 260727A: AstroSat CZTI detection
- GRB 260727A: Kilonova-Catcher optical upper limit
- GRB 260727A: LCO optical upper limits
- Fermi GRB 260726A: Global MASTER-Net observations report
- GRB 260726A: SVOM detection of a burst
- IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
- EP260723a: further EP-FXT follow-up observation
- EP260725a: EP-FXT follow-up observation and association with a bright flaring star
- GRB 260616A: cubesat Avion detection
- EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
- GRB 260602B: cubesat Avion detection
- GRB 260601A: cubesat Avion detection
- EP260723a: EP-FXT follow-up observation
- IPN triangulation of GRB 260706B
- GRB 260718A: SVOM/ECLAIRs refined analysis
- EP260723a: SVOM/VT optical observation
- EP260723a: COLIBRÍ optical observations
- EP260723a: NOT optical conterpart confirmation
- EP260723a: Liverpool Telescope likely optical counterpart
- IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
- Konus-Wind detection of GRB 260721A
- IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260721A: NuSTAR detection of prompt emission
- Konus-Wind detection of GRB 260714B
- SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
- GRB 260705A: Retraction of optical counterpart
- GRB 260714B: Insight-HXMT/HE detection
- GRB 260718A: EP-FXT follow-up observation
- Fermi GRB 260718A: Global MASTER-Net observations report
- GRB 260718A: LCO optical upper limits
- GRB 260711A: SVOM/GRM observation
- GRB 260710A: SVOM/GRM observation
- GRB 260718A: Fermi GBM Observation
- GRB 260718A : GRANDMA and KNC upper limits
- GRB 260718A: SVOM/VT optical upper limits
- GRB 260718A: SVOM/VT optical upper limits from VHF data
- GRB 260718A: SVOM detection of a burst
- GRB 260714B: SVOM/GRM observation
- GRB 260310A / AT2026fgk: Late-time Chandra Detection
- GRB 260714B: GECAM-B observation of a burst
- GRB 260618B: EP-FXT follow-up observation upper limit
- GRB 260714B: COLIBRÍ optical counterpart candidate
- IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert
- SVOM sb26071506: Global MASTER-Net observations report
- IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
- EP260703a: SVOM/ECLAIRs Upper Limit
- GRB 260710A: AstroSat CZTI detection
- GRB 260709A: AstroSat CZTI detection
- GRB 260714B: AstroSat CZTI detection