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"27783 results found.
- GRB 260510C: MAXI/GSC detection
- Fermi GBM Sub-Threshold Detection of GRB 260510B
- GRB 260510D: Fermi GBM Final Real-time Localization
- GRB 260510B: GOTO early upper limit
- GRB 260510C: SVOM detection of a burst
- GRB 260510C: Fermi GBM Final Real-time Localization
- EP260509a: Einstein Probe detection of an X-ray transient
- GRB 260510B: SVOM detection of a burst
- GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
- GRB 260510A: Fermi GBM Final Real-time Localization
- GRB 260509A: LCO optical counterpart detection
- GRB 260509A: SVOM detection of a burst
- GRB 260506B: AstroSat CZTI detection
- GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
- EP260507a: further Liverpool Telescope observations
- GRB 260507A: Fermi GBM Final Real-time Localization
- EP260507a: GOTO optical counterpart detection
- EP260507a: TRT optical counterpart detection
- EP260507a: Einstein Probe detection of an X-ray transient
- GRB 260504B: AstroSat CZTI detection
- GRB 260506B: Fermi GBM Final Real-time Localization
- GRB 260506A: Fermi GBM Final Real-time Localization
- GRB 260430B: Glowbug gamma-ray detection
- Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
- Konus-Wind detection of GRB 260504B (short/hard)
- GRB 260504B: GECAM-B detection
- GRB 260430B: AstroSat CZTI detection of a long burst
- GRB 260504B: SVOM/MXT refined analysis and potential detection
- IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
- Konus-Wind detection of GRB 260415C
- Konus-Wind detection of GRB 260411C
- IPN triangulation of GRB 260429A
- IPN triangulation of GRB 260428A
- GRB 260504B: AST3-2 i-band upper limit
- GRB 260504B: SVOM detection of a short burst
- GRB 260504A: Fermi GBM Final Real-time Localization
- GRB 260503A: Fermi GBM Final Real-time Localization
- GRB 260502A: Fermi GBM Final Localization
- GRB 260429B / EP260429a: AstroSat CZTI detection
- EP260502a: BOOTES-7: early optical upper limit
- EP260502a: Einstein Probe detection of an X-ray transient
- SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
- GRB 260424B: AstroSat CZTI detection
- GRB 260429A: Fermi GBM Detection
- EP260430a: Einstein Probe detection of an X-ray transient
- EP260429a: EP-WXT detection of a fast X-ray transient
- GRB 260429A: Fermi GBM Final Real-time Localization
- GRB 260428A: GECAM-B detection of a possible long duration Type I burst
- GRB 260428A: AstroSat CZTI detection
- GRB 260424B: Glowbug gamma-ray detection of a short burst
- Konus-Wind detection of GRB 260424B
- GRB 260428A: Fermi GBM Final Real-time Localization
- GRB 260424C: Fermi GBM Final Localization
- IPN triangulation of GRB 260424B (short)
- GRB 260424B: SVOM/GRM detection of a short burst
- IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
- GRB 260401A: cubesat Avion detection
- GRB 260424A: AstroSat CZTI detection of a long burst
- GRB 260421B: Kilonova-Catcher optical afterglow detection
- GRB 260421B: Insight-HXMT/HE detection
- EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
- GRB 260419A: AstroSat CZTI detection
- GOTO26djh/AT2026jpw: ATCA radio detection
- GRB 260421B: LCO optical counterpart detection
- GRB 260421A: AstroSat CZTI detection
- GOTO26djh/AT2026jpw: radio detection at 15GHz
- GRB 260310A: Late-time Chandra X-ray Detection
- GRB 260418A: Insight-HXMT/HE detection
- GRB 260415A: CALET Gamma-Ray Burst Monitor detection
- GRB 260415B: CALET Gamma-Ray Burst Monitor detection
- GRB 260421C: Fermi GBM Final Real-time Localization
- GRB 260421B: BOOTES-7 early optical afterglow detection
- GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
- GRB 260421B: TRT optical counterpart detection
- GRB 260421B: SVOM detection of a long burst
- GRB 260421B: Fermi GBM Final Real-time Localization
- GRB 260421A: Fermi GBM Final Real-time Localization
- EP260416a: Optical follow-up observations with Kinder
- GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
- EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
- GRB 260419B: Fermi GBM Final Real-time Localization
- GRB 260419A: Fermi GBM Final Real-time Localization
- EP260416a: Ondrejov D50 optical detection
- GRB 260418B: Fermi GBM Final Real-time Localization
- EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260418A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 260411B
- GRB 260417B: Fermi GBM Final Real-time Localization
- GRB 260417A: AstroSat CZTI detection
- IPN triangulation of GRB 260411B
- EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
- EP260417a: TRT optical counterpart detection
- EP260417a: Einstein Probe detection of an X-ray transient
- EP260417b: Einstein Probe detection of a fast X-ray transient
- GRB 260414A: Insight-HXMT/HE detection
- EP260416a: WFST optical observations and rebrightening
- GRB 260417A: Fermi GBM Final Real-time Localization
- GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
- GRB 260415B: Glowbug gamma-ray detection