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"28072 results found.
- GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
- GRB 250424A: BlackGEM optical afterglow detection
- GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
- GRB 250424A: likely host galaxy
- GRB 250424A: DDOTI Afterglow Detection
- GRB 250424A: REM optical/NIR afterglow detection
- GRB 250424A: Swift detection of a burst with an optical counterpart
- Swift GRB 250424A: Global MASTER-Net OT detection
- EP250421a: Nickel optical upper limit
- EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
- SVOM/sb25042207: XRT observations
- SVOM/sb25042207: BOOTES-2 early optical upper limit
- GRB 250421A: AstroSat CZTI detection
- SVOM/sb25042207: SVOM detection of an X-ray transient
- GRB250419A: VLA radio detection
- IceCube-250421A: DDOTI Detection of the LAST Candidate
- GRB 250419A: Mephisto Multi-band Optical Detection
- IC-250421A: LAST optical observations of the IceCube neutrino candidate
- EP250421a: NOT optical observations
- GRB 250419A: Optical Observations via Virtual Telescope Project
- EP250421a: REM optical upper limit
- EP250421a: Swift/XRT counterpart detection
- GRB 250421B: AstroSat CZTI detection of a bright long burst
- EP250421a: Einstein Probe detection of an X-ray transient
- EP250421a: Mephisto optical counterpart confirmation
- IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250421A: Fermi GBM Final Real-time Localization
- GRB 250419A: Liverpool Telescope observations
- GRB 250419A: JinShan optical observations
- GRB 250419A: LCO optical afterglow multi-band observations
- GRB 250419A: AKO Optical Afterglow Detection
- GRB 250419A: MASTER optical afterglow observation
- GRB 250419A: Swift-XRT localisation
- GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
- GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
- GRB 250419A: Swift-XRT refined Analysis
- GRB 250419A: GOTO optical counterpart detection
- GRB 250419A: KAIT optical afterglow observations
- GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- GRB 250419A: SVOM detection of a soft burst
- Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
- EP250416a: Swift/XRT counterpart fading
- EP250416a: refined EP-WXT and EP-FXT analysis
- Konus-Wind detection of GRB 250403A
- EP20250416a: Swift/XRT counterpart detection
- EP250416a: Gemini South-GMOS optical counterpart
- EP250416a: GSP optical upper limit
- EP250416a: Einstein Probe detection of an X-ray transient
- IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250416B: Fermi GBM Final Real-time Localization
- GRB 250416A: Fermi GBM Final Real-time Localization
- SVOM/sb25041603: SVOM detection of an X-ray transient
- GRB 250413A: AstroSat CZTI detection
- GRB 250412A: AstroSat CZTI detection
- EP250404a: Nanshan 0.43m Telescope optical observatios
- GRB 250411A: Fermi GBM Final Real-time Localization
- GRB 250407A: Continued KAIT/Nickel optical observations
- GRB 250320B: cubesat Avion detection
- IceCube-250406A: Swift-XRT observations
- IPN triangulation of GRB 250407A
- GRB 250407A: LCO detection of a fading optical counterpart
- EP250407a: Swift-XRT observations
- Konus-Wind detection of GRB 250407A
- GRB 250407A: SVOM/GRM observation of a bright long burst
- GRB 250407A: EP-WXT afterglow detection
- EP250407a: EP-WXT detection of a fast X-ray transient
- GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250407A: KAIT Optical Afterglow Candidate
- GRB 250407A: Fermi GBM Detection
- GRB 250407A: Swift-XRT afterglow detection
- GRB 250407A: Swift ToO observations
- GRB 250407A: SRG/ART-XC afterglow detection
- Konus-Wind detection of GRB 250406B (short/hard)
- GRB 250407A: Fermi GBM Final Real-time Localization
- IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- GRB 250406A: AstroSat CZTI detection
- GRB 250406A: Fermi GBM Final Real-time Localization
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
- EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
- Konus-Wind detection of GRB 250404A / EP250404a
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- 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 / GRB250404A: Ondrejov D50 optical afterglow detection
- EP250404a: LCO optical counterpart detection
- GRB 250403A: Montarrenti Observatory optical detection
- GRB 250404A: Fermi GBM Detection
- GRB 250403A: KAIT optical observations
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- EP250404a: Xinglong-2.16m spectroscopic redshift
- GRB 250327B: VIRT Optical Upper Limit
- EP250404a: Mephisto multi-band optical detection