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"21788 results found.
- Fermi trigger No 784034269: Global MASTER-Net observations report
- EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
- LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
- GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
- GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
- Fermi GBM Sub-Threshold Detection of GRB 251105B
- GRB 251103B: Swift/UVOT Upper Limits
- Fermi GRB 251105A: Global MASTER-Net observations report
- EP251102a: FTW optical and NIR observations
- GRB 251103A: WFST optical observations
- EP251102a: OHP/T193 optical observations
- GRB 251103A: OHP/T193 optical observations
- GRB 251103A: KAIT optical observations
- GRB 251103B: Nanshan/HMT optical upper limit
- GRB 251013C: 7DT detection and Medium-band SED of Afterglow
- GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
- Fermi GRB 251103A: Global MASTER-Net observations report
- EP251102a: NIR observations with WINTER
- GRB 251103A: J-band detection with WINTER
- Swift GRB 251103B: Global MASTER-Net observations report
- GRB 251103A: Kilonova-Catcher optical afterglow detection
- GRB 251103A: Swift/UVOT Detection
- GRB 251103A: Swift-XRT afterglow detection
- GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 251025B: OHP/T193 optical upper limit
- EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
- GRB 251103A: LCO optical observation
- EP251102.890: COLIBRÍ optical counterpart candidate
- GRB 251103A: GOTO optical afterglow detection
- GRB 251103A: NOT optical afterglow candidate
- Fermi GRB 251102A: Global MASTER-Net observations report
- GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
- IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
- GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
- GRB 251022A: Swift-XRT confirmation of fading
- GRB 251026B: LBT near-infrared observations
- GRB 251026A/EP251026a: EP-FXT follow-up observation
- GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
- Fermi GRB 251028B: Global MASTER-Net observations report
- GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
- GRB251026B: PRIME H-band upper limit
- GRB251025B: 3.6m DOT Optical Observations
- GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
- GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
- Fermi-LAT Gamma-ray Observations of IceCube-251025A
- GRB 251023B: Swift-UVOT Upper Limits
- GRB 251027A: Swift-XRT observations
- GRB 251026B: Swift ToO observations
- GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
- GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
- GRB 251017A: INASAN-Kislovodsk optical observations
- GRB 251025B: Mondy optical observations
- GRB 251025B: Kilonova-Catcher optical afterglow detection
- GRB 251027A: SVOM detection of a faint burst
- GRB 251026B: Tentative GOTO optical counterpart candidate
- EP251023a: Mondy optical observations
- GRB 251025B: MAO/AZT-22 optical observations
- Fermi GRB 251026B: Global MASTER-Net observations report
- Fermi GRB 251025C: Global MASTER-Net observations report
- GRB 251026A: Swift-XRT observations
- GRB 251025B: OHP/T193 optical detection
- GRB 251025B: J-band detection with WINTER
- GRB 251026A: SVOM/C-GFT upper limit
- IceCube-251025A: DDOTI Optical Upper Limit
- GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
- GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
- GRB 251025B: GROWTH-India Telescope optical observations
- GRB 251024A: Swift/UVOT Upper Limits
- GRB 251025B: Swift-XRT afterglow detection
- IceCube Alert 251025.57: Global MASTER-Net observations report
- GRB 251025A (sb25102501): stellar flare confirmed
- GRB 251025B: SVOM/VT optical observations with VHF data
- GRB 251025B: SVOM/C-GFT optical counterpart detection
- GRB 251003A: VLA Detection
- GRB 251022A: KAIT optical observations
- Swift GRB 251024A: Global MASTER-Net observations report
- GRB 251022A: COLIBRÍ Further Multi-frequency Optical Observations
- EP251023a: MAO/AZT-22 optical observations
- GRB 251023B: OHP/T193 optical observations
- EP251023a: OHP/T193 optical observations
- EP251023b/GRB 251023B: JinShan optical observation
- GRB 251022A: Swift-XRT detection of GOTO25iym
- EP251023b: Global MASTER-Net observations report
- GRB 251022A: GROWTH-India Telescope optical observations
- GRB 251023C: Swift/BAT-GUANO localization skymap of a burst
- EP251023a: GROWTH-India Telescope optical observations
- GRB 251022A: Swift/BAT-GUANO localization skymap of a burst
- EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
- EP251023a: Global MASTER-Net observations report
- GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
- EP#01709247298: Swift-XRT counterpart detection
- EP251023a: COLIBRÍ optical observations
- GRB 251013C: further SAO RAS optical observations
- EP251023a: Keck/LRIS spectroscopic redshift z=2.232
- GRB 251022A: COLIBRÍ optical observations
- GRB 251013C: ISON-Castelgrande observatory optical observations
- GRB 251022A: MASTER OT detection
- GRB 251022A: DDOTI Optical Detection
- Fermi GRB 251023A: Global MASTER-Net observations report