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"
23838 results found.
- GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250430A: KAIT optical observations
- GRB 250430A: NUTTelA-TAO Early Measurements
- EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
- 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
- GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
- 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
- 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
- Swift GRB250430.73: Global MASTER-Net observations report
- EP250428b: FTW optical and NIR observations
- EP250427a/GRB250427A: HCT optical follow-up
- EP250427a / GRB 250427A: OHP/T193 continued photometric observations
- SVOM/sb25043004: SVOM detection of a X-ray transient
- Fermi trigger No 767623859: Global MASTER-Net observations report
- EP250428b: GROWTH-India telescope optical upper limit
- EP250428b: Global MASTER-Net observations report
- EP250427a / GRB 250427A: OHP/T193 photometric observations
- EP250427a: EP-FXT follow-up observations
- EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
- EP250427a: Lesedi optical counterpart detection
- EP250427A: COLIBRÍ Continuing Optical Observations
- GRB250427A/EP250427a GIT optical afterglow 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
- GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
- EP250427A: COLIBRÍ Optical Detection
- EP250427a: TRT optical counterpart detection
- EP250427a: Global MASTER-Net observations report
- IceCube Alert 250426.74: Global MASTER-Net observations report
- 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
- GRB 250419A: Mondy Optical Observations
- GRB 250424A: Swift/UVOT Detection
- Konus-Wind detection of GRB 250424A
- GRB 250424A: Kilonova-Catcher optical afterglow detection
- GRB 250419a: Continued Liverpool Telescope observations
- GRB 250419A: Liverpool Telescope optical upper limit
- GRB 250330B: GRBAlpha detection
- GRB 250424A: Swift-XRT refined Analysis
- 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: 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 GRB250424A: Global MASTER-Net observations report
- Swift GRB250424A: Global MASTER-Net OT detection
- EP250421a: Nickel optical upper limit
- EP250421a: Upper limits from Fermi-GBM Observations
- SVOM/sb25042207: XRT observations
- SVOM/sb25042207: GOTO optical upper limits
- SVOM/sb25042207: SVOM detection of an X-ray transient
- IceCube-250421A: DDOTI Detection of the LAST Candidate
- GRB 250419A: Mephisto Multi-band Optical Detection
- EP250421a: NOT optical observations
- EP250421a: REM optical upper limit
- EP250421a: Swift/XRT counterpart detection
- EP250421A: COLIBRÍ Optical Upper Limit
- GRB 250419A: Mondy Continued Optical Observations
- Fermi GRB 250421A: Global MASTER-Net observations report
- EP250421a: Global MASTER-Net observations report
- EP250421a: Einstein Probe detection of an X-ray transient
- EP250421a: Mephisto optical counterpart confirmation
- IceCube Alert 250421.71: Global MASTER-Net observations report
- EP250421a: JinShan likely optical counterpart
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250421A: Fermi GBM Final Real-time Localization
- GRB 250419A: Liverpool Telescope observations
- GRB 250419A: LCO optical observation
- GRB 250419A: JinShan optical observations
- GRB 250419A: SVOM/VT optical continuous observations
- GRB 250419A: SVOM/C-GFT optical observations
- GRB 250419A: Swift/UVOT Follow up
- GRB 250419A: LCO optical afterglow multi-band observations
- GRB 250419A: Mondy and AbAO Optical Observations
- GRB 250419A: AKO Optical Afterglow Detection
- GRB 250419A: MASTER optical afterglow observation
- GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
- GRB 250419A: Swift-XRT refined Analysis
- GRB 250419A: GOTO optical counterpart detection
- 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