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"28063 results found.
- Fermi GBM Sub-Threshold Detection of GRB 260915A
- GRB 260915A: SVOM detection of a burst
- Fermi GBM Sub-Threshold Detection of GRB 260914A
- GRB 260914A: SVOM/VT optical observation from VHF data
- GRB 260914A: SVOM detection of a burst
- GRB 260818A: Continued ATCA observations
- GRB 260913A: SVOM detection of a faint burst
- GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
- GRB 260910B: GOTO tentative optical counterpart candidates
- GRB 260909A: Swift ToO observations
- GRB 260910B: Fermi GBM Final Real-time Localization
- GRB 260903A: Swift-XRT observations
- EP260806a: VLA+ALMA radio detections
- GRB 260909A: OHP/T193 z-band upper limit
- GRB 260910A: Fermi GBM Final Real-time Localization
- EP260806a: NOEMA detection
- EP260623a: NOEMA detections
- GRB 260909A: Mondy optical observations and afterglow candidate
- GRB 260909A: SVOM detection of a burst
- The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
- GRB 260907A: Glowbug gamma-ray detection of a likely short burst
- GRB 260903A: Swift ToO observations
- GRB 260907B: Fermi GBM Final Real-time Localization
- GRB 260907A: Fermi GBM Final Real-time Localization
- EP260903a: EP-FXT follow-up observation
- GRB 260830A: GECAM-B detection of a burst
- EP260903a: EP-WXT detection of a fast X-ray transient
- GRB 260830A: Insight-HXMT/HE detection
- GRB 260903A: OHP/T193 optical afterglow detection
- GRB 260903A: NOT optical observations and afterglow fading
- NuSTAR Transient 260828: SOAR Optical Upper Limits
- GRB 260903A: Retraction of optical counterpart of GCN 45501
- GRB 260903A: LCO optical counterpart detection
- GRB 260827A: Insight-HXMT/HE detection
- GRB 260903A: SVOM detection of a soft faint burst
- EP260901a: EP-FXT follow-up observation
- Konus-Wind detection of GRB 260829A
- GRB 260818A: ATCA detection of a candidate radio counterpart
- EP260830a: EP-FXT follow-up observation
- NuSTAR Transient 260828: LCO Optical Upper Limits
- EP260901a: EP-WXT detection of a fast X-ray transient
- GRB 260829A: AstroSat CZTI detection
- GRB 260830A: NuSTAR detection of prompt emission
- EP260830a: EP-WXT detection of a fast X-ray transient
- NuSTAR 260828: a 1100s hard X-ray transient
- GRB 260831B: SVOM detection of a possible burst
- IPN triangulation of GRB 260829A
- GRB 260827A: Glowbug gamma-ray detection
- EP260727a: ATCA 10 GHz detection
- GRB 260831A: Fermi GBM Final Real-time Localization
- GRB 260829A: Fermi GBM Detection
- GRB 260825A: AstroSat CZTI detection
- GRB 260829A: Fermi GBM Final Real-time Localization
- GRB 260818B: VLT optical and nIR observations
- IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
- The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
- GRB 260827A: Fermi GBM Final Real-time Localization
- GRB 260818B: 6 GHz VLA observations
- GRB 260818B: SVOM/VT optical upper limit and continuous observations
- GRB 260807A: EP-FXT follow-up observations
- GRB 260822A: SVOM/VT optical upper limits
- GRB 260825A: Fermi GBM Final Real-time Localization
- IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 260822A: PRIME near-infrared upper limits from multiple epochs
- GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
- GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
- EP260822a: EP-FXT non-detection and upper limit
- GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
- GRB 260822A: GOTO optical counterpart detection
- GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
- EP260822a: Einstein Probe detection of a fast X-ray transient
- The EP-WXT trigger 01709287395 is likely a flaring star
- GRB260822B: Fermi GBM Final Localization
- GRB 260822A: SVOM detection of a short burst
- GRB 260818B: SVOM/C-GFT optical upper limit
- EP260731a: SVOM/ECLAIRs detection through offline targeted search
- GRB 260820A: Insight-HXMT/HE detection
- IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
- EP detected a brightening of LMXB 1ES 1735-26.9
- GRB260820A: Fermi GBM Final Real-Time Localization
- GRB 260818B: Insight-HXMT detection
- GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 260818B: SVOM detection of a short burst
- GRB 260810A: Insight-HXMT/HE detection
- GRB 260818A: SVOM possible detection of a long and faint GRB
- EP260806a: SVOM/ECLAIRs detection through targeted search
- EP260806a: WFST optical observations
- EP260812b: Optical upper limit with Kinder
- GRB 260805D: SVOM/GRM detection of a possible magnetar burst
- GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
- GRB 260813A: Fermi GBM Final Real-time Localization
- EP260812b: Liverpool Telescope observations
- EP260812b: GOTO detection of the optical counterpart
- EP260812b: Einstein Probe detection of an X-ray transient
- EP trigger #01709278129 (EP260812b?): NOT optical counterpart
- Fermi GBM Sub-Threshold Detection of GRB 260809A
- GRB 260810A: Glowbug gamma-ray detection
- GRB 260810A: AstroSat CZTI detection of a long burst
- EP260812a: Einstein Probe detection of an X-ray transient
- GRB 260808B: SVOM/VT optical re-brightening at day 3