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"
24571 results found.
- GRB 250430A: DDOTI Optical Observations
- GRB 250430A: Leavitt Observatory optical upper limit
- GRB 250430A: Bassano Bresciano Observatory upper limit
- GRB 250430A : MITSuME Akeno optical upper limits
- SVOM/sb25043004: EP-FXT observations
- EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
- GRB 250424A: CALET Gamma-Ray Burst Monitor detection
- IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250430A: AKO Optical Afterglow Detection
- GRB 250430A: Kanata optical upper limit
- EP 250427A: Optical counterpart detection by LCO.
- GRB 250430A: Swift detection of a burst with optical counterpart
- EP250427a/GRB250427A: HCT optical follow-up
- SVOM/sb25043004: SVOM detection of a X-ray transient
- EP250428b: GROWTH-India telescope optical upper limit
- EP250428b: SAO RAS optical upper limit
- EP250428b: LAST optical upper limit
- GRB 250427A: Swift/UVOT Detection
- EP250428b: Global MASTER-Net observations report
- EP250428b: Einstein Probe detection of a fast X-ray transient
- Fermi-LAT Gamma-ray Observations of IceCube-250426A
- 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: REM optical/NIR afterglow detection
- GRB 250424A: LCO optical observation
- GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
- EP250427A: COLIBRÍ Optical Detection
- EP250427a: TRT optical counterpart detection
- EP250427a: Einstein Probe detection of a fast X-ray transient
- GRB 250424A: Swift-BAT refined analysis
- GRB 250424A: SVOM/GRM observation of a long burst
- GRB 250424A: PRIME near-infrared detection
- GRB 250424A: WINTER J-band detection
- GRB 250424A: EIRSAT-1 GMOD 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
- Fermi-LAT gamma-ray observations of IceCube-250421A
- GRB 250424A: Skynet Optical Observations
- GRB 250424A: Kilonova-Catcher optical afterglow detection
- GRB 250330B: GRBAlpha detection
- GRB 250424A: Swift-XRT refined Analysis
- GRB 250424A: Enhanced Swift-XRT position
- GRB 250424A: AstroSat CZTI detection of a bright long burst
- 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
- Swift GRB250424A: Global MASTER-Net OT detection
- LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
- EP250421a: Nickel optical upper limit
- EP250421a: Upper limits from Fermi-GBM Observations
- 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: COLIBRÍ Optical Upper Limit
- GRB 250419A: Mondy Continued Optical Observations
- 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-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
- EP250416a: Swift/XRT counterpart fading
- EP20250416a: Swift/XRT counterpart detection
- IceCube-250416A: DDOTI Optical Observations
- EP250416a: Gemini South-GMOS optical counterpart
- SVOM/sb25041603 is not a GRB
- EP250416a: GSP optical upper limit
- 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
- GRB 250413A: AstroSat CZTI detection