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"14851 results found.
- GRB 250404A / EP250404a: NOT optical observations
- GRB 250331D: Swift-XRT afterglow detection
- GRB 250404B: AstroSat CZTI detection of a short burst
- GRB 250403A: AstroSat CZTI detection
- EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
- EP250404a: REM optical/NIR observations
- EP250404a: Seimei/TriCCS optical counterpart detection
- EP250404A: COLIBRÍ/DDRAGO Optical Observations
- EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
- EP250404a: LCO optical counterpart detection
- EP250404a: Xinglong decaying optical counterpart
- GRB 250403A: Montarrenti Observatory optical detection
- GRB 250404A: Fermi GBM Detection
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- EP250404a: Xinglong-2.16m spectroscopic redshift
- GRB 250327B: VIRT Optical Upper Limit
- EP250404a: Mephisto multi-band optical detection
- EP250404a: BOOTES-4/JGT optical afterglow detection
- EP250404a: Nanshan/HMT optical counterpart detection
- EP250404a: Einstein Probe detection of an X-ray transient
- GRB 250404A: Fermi GBM Final Real-time Localization
- GRB 250403A: Swift/UVOT Detection
- GRB 250402A: Swift/UVOT Upper Limits
- GRB 250403A: REM NIR afterglow detection
- GRB 250403A: LCO optical counterpart detection
- IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
- GRB 250402A: EP-FXT afterglow detection
- GRB 250403A: Optical counterpart detection by LCO.
- GRB 250322A: 10 GHz VLA radio upper limits
- GRB 250403A: 1.6m Mephisto multi-band optical detection
- GRB 250403A: GOTO detection of the optical afterglow
- GRB 250403A : SVOM detection of a burst
- GRB 250403A: Fermi GBM Final Real-time Localization
- GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
- GRB 250402A: LCO optical counterpart detection
- EP250402a: Einstein Probe detection of a fast X-ray transient
- GRB 250402B: AstroSat CZTI detection of a short burst
- GRB 250402A: SVOM detection of a burst
- GRB 250314A: ALMA detection
- GRB 250329A: Swift/UVOT Upper Limit
- GRB 250327B: Swift/UVOT Detection
- GRB 250219A: NOT candidate host galaxy detection
- GRB 250322B: GRBAlpha detection
- GRB 250322B possible detection by the AstroSat Satellite
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
- GRB 250330B: EIRSAT-1 GMOD Detection
- GRB 250331E: Fermi GBM Final Real-time Localization
- GRB 250329B: CAHA 2.2m telescope optical limit
- Konus-Wind detection of GRB 250327B
- GRB 250320C : SVOM detection of a burst through offline search
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250330A: VLT/FORS2 Afterglow Detection
- GRB 250328A: Swift/UVOT Detection
- GRB 250331D: Fermi GBM Final Real-time Localization
- GRB 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- GRB 250331A: MAXI/GSC detection
- SVOM/sb25033102: SVOM detection of an X-ray transient
- GRB 250314A: VLA detection
- GRB 250330B: Fermi GBM Final Real-time Localization
- GRB 250330A: BOOTES-7 early optical upper limit
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250328A: 1.6m Mephisto optical observations
- GRB 250330A: Fermi GBM Final Localization
- IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- GRB 250327B: ALMA detection
- GRB 250327B: VLA detection
- GRB250329A: REM optical afterglow detection
- GRB 250329B: SVOM detection of a faint transient
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250329A: VLT/X-shooter redshift z = 2.921
- GRB 250329A: SVOM detection of a burst
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: MASTER detection of OT rebrightening
- GRB 250327B: LCO optical counterpart detection
- GRB 250328A: SVOM detection of a burst
- GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
- EP250315a: Pan-STARRS r and i-band imaging and photometry
- GRB 250327b: Liverpool Telescope optical observations
- GRB 250327B: Las Cumbres optical counterpart detection
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327B: NOT spectroscopic redshift z = 3.035
- GRB 250327B: GOTO optical counterpart detection
- GRB 250327B: SVOM detection of a burst
- FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: Swift detection of a burst
- GRB 250327A: Fermi GBM Final Real-time Localization
- Konus-Wind detection of GRB 250322A (short)
- IPN triangulation of GRB 250322B
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
- EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
- GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
- EP250321a: TNOT Observation of Optical Counterpart