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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
23209 results found.
- EP250428b: refined analysis of the EP-FXT follow-up observation
- EP250428b: GROWTH-India telescope optical upper limit
- EP250428b: SAO RAS optical upper limit
- EP250428b: LAST optical upper limit
- GRB 250427A: Swift/UVOT Detection
- EP250428b: Einstein Probe detection of a fast X-ray transient
- Fermi-LAT Gamma-ray Observations of IceCube-250426A
- EP250427a: EP-FXT follow-up observations
- EP250427a: Lesedi optical counterpart detection
- EP250427A: COLIBRÍ Continuing Optical Observations
- GRB250427A/EP250427a GIT optical afterglow detection:
- EP250427a: LT optical counterpart detection
- GRB 250427A: Swift-XRT refined Analysis
- EP250427a / GRB 250427A: LCO optical counterpart detection
- EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
- EP250427a: REM optical/NIR afterglow detection
- GRB 250424A: LCO optical observation
- EP250427A: COLIBRÍ Optical Detection
- EP250427a: TRT optical counterpart detection
- EP250427a: Einstein Probe detection of a fast X-ray transient
- IceCube Alert 250426.74: Global MASTER-Net observations report
- GRB 250424A: SVOM/GRM observation of a long burst
- GRB 250424A: PRIME near-infrared detection
- GRB 250424A: WINTER J-band detection
- IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250419A: Mondy Optical Observations
- GRB 250424A: Swift/UVOT Detection
- Konus-Wind detection of GRB 250424A
- Fermi-LAT gamma-ray observations of IceCube-250421A
- GRB 250424A: Skynet Optical Observations
- GRB 250424A: Kilonova-Catcher optical afterglow detection
- GRB 250419a: Continued Liverpool Telescope observations
- GRB 250419A: SVOM/ECLAIRs refined analysis
- GRB 250424A: Swift-XRT refined Analysis
- GRB 250424A: Enhanced Swift-XRT position
- GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
- GRB 250424A: BlackGEM optical afterglow detection
- GRB 250424A: DDOTI Afterglow Detection
- GRB 250424A: REM optical/NIR afterglow detection
- GRB 250424A: Swift detection of a burst with an optical counterpart
- LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
- EP250421a: Nickel optical upper limit
- SVOM/sb25042207: XRT observations
- SVOM/sb25042207: BOOTES-2 early optical upper limit
- SVOM/sb25042207: SVOM detection of an X-ray transient
- IceCube-250421A: DDOTI Detection of the LAST Candidate
- GRB 250419A: Mephisto Multi-band Optical Detection
- GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- 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
- EP250421A: COLIBRÍ Optical Upper Limit
- GRB 250419A: Mondy Continued Optical Observations
- EP250421a: Einstein Probe detection of an X-ray transient
- EP250421a: Mephisto optical counterpart confirmation
- IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
- EP250421a: JinShan likely optical counterpart
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250419A: LCO optical observation
- GRB 250419A: JinShan optical observations
- GRB 250419A: SVOM/C-GFT optical observations
- GRB 250419A: Swift/UVOT Follow up
- GRB 250416C / EP250416a: SVOM/GRM observation of a burst
- GRB 250419A: LCO optical afterglow multi-band observations
- GRB 250419A: Mondy and AbAO Optical Observations
- GRB 250419A: AKO Optical Afterglow Detection
- Fermi-LAT Gamma-ray Observations of IceCube-250416A
- GRB 250419A: Swift-XRT refined Analysis
- GRB 250419A: KAIT optical afterglow observations
- GRB 250419A: SVOM/VT optical bright counterpart confirmation
- 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
- IceCube-250416A: DDOTI Optical Observations
- EP250416a: Gemini South-GMOS optical counterpart
- SVOM/sb25041603 is not a GRB
- EP250416a: Einstein Probe detection of an X-ray transient
- SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
- SVOM/sb25041603: SVOM detection of an X-ray transient
- IceCube 250414.324: DDOTI Optical Observations
- EP250404a: Nanshan 0.43m Telescope optical observatios
- GRB 250411A: DDOTI Optical Observations
- GRB 250314A: e-MERLIN observations
- GRB 250407A: Mondy and AbAO Optical Observations
- EP250227a: Further NOT optical observations
- GRB 250320B: cubesat Avion detection
- IceCube-250406A: Swift-XRT observations
- GRB 250407A: LCO detection of a fading optical counterpart
- Fermi-LAT gamma-ray observations of IceCube-250406A
- EP250407a: Swift-XRT observations
- IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
- Konus-Wind detection of GRB 250407A
- GRB 250407A: SVOM/GRM observation of a bright long burst