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"
3820 results found.
- Fermi GRB 250510C: Global MASTER-Net observations report
- Fermi GRB 250510B: Global MASTER-Net observations report
- GRB 250509A: Fermi GBM Final Real-time Localization
- GRB 250506A: NOT optical upper limits
- GRB 250506A: Swift XRT observations and possible counterpart detection
- GRB 250506A: TRT optical observations
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
- GRB 250504A: MeerLICHT optical afterglow detection
- Fermi GRB 250504A: Global MASTER-Net observations report
- Swift GRB250504.98: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250429A
- GRB 250430A: Leavitt Observatory optical upper limit
- GRB 250430A : MITSuME Akeno optical upper limits
- IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250430A: AKO Optical Afterglow Detection
- Swift GRB250430.73: Global MASTER-Net observations report
- EP250427a/GRB250427A: HCT optical follow-up
- EP250428b: SVOM/VT upper limit
- EP250428b: SAO RAS optical upper limit
- EP250428b: LAST optical upper limit
- IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
- EP250428b: Global MASTER-Net observations report
- EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
- EP250427a: TRT optical counterpart detection
- EP 250427a: BOOTES-7 optical afterglow candidate
- GRB 250424A: SVOM/VT optical observation
- GRB 250419A: Mondy Optical Observations
- GRB 250424A: Swift/UVOT Detection
- GRB 250424A: Swift detection of a burst with an optical counterpart
- GRB250419A: VLA radio detection
- GRB 250419A: Mephisto Multi-band Optical Detection
- GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- GRB 250419A: Optical Observations via Virtual Telescope Project
- IceCube Alert 250421.71: Global MASTER-Net observations report
- EP250421a: JinShan likely optical counterpart
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250419A: Swift/UVOT Follow up
- GRB 250419A: AKO Optical Afterglow Detection
- GRB 250419A: SVOM/VT optical bright counterpart confirmation
- GRB 250419A: SVOM detection of a soft burst
- GRB 250412A: AstroSat CZTI detection
- EP250404a: Nanshan 0.43m Telescope optical observatios
- Fermi trigger No 766148493: Global MASTER-Net observations report
- Fermi trigger No 766173972: Global MASTER-Net observations report
- Fermi GRB 250407A: Global MASTER-Net observations report
- Fermi GRB 250406A: Global MASTER-Net observations report
- GRB 250402A: Mondy optical observations
- EP250402a: Einstein Probe detection of a fast X-ray transient
- Fermi GRB 250331E: Global MASTER-Net observations report
- GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
- IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
- SVOM/sb25033102: SVOM detection of an X-ray transient
- GRB 250328A: 1.6m Mephisto optical observations
- GRB 250327B: ALMA detection
- GRB 250327B: VLA detection
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- GRB250329A: REM optical afterglow detection
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
- GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
- GRB 250329A: SVOM/VT optical counterpart confirmation
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: further optical observations by LCOGT
- GRB 250327B: SVOM/VT optically bright counterpart
- GRB 250327B: SAO RAS optical candidate
- IPN triangulation of GRB 250322B
- EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
- FRB 250316A: DDOTI Continued Optical Observations
- GRB 250322A: MASTER optical observation
- FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
- EP250321a: SVOM/VT optical observation
- GRB 250320B: AstroSat CZTI detection
- Fermi GRB 250320B: Global MASTER-Net observations report
- GRB 250321A: GOTO optical upper limits
- GRB 250319B: Fermi GBM Final Localization
- Fermi trigger No 763933627: Global MASTER-Net observations report
- GRB 250316A: Swift/UVOT Upper Limits
- GRB 250317A: Fermi GBM Final Real-time Localization
- Fermi GRB 250313A: Global MASTER-Net observations report
- EP250311a/GRB 250311A: EP-FXT follow-up observation
- Fermi GRB 250312B: Global MASTER-Net observations report
- IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
- GRB 250309B / AT2025dws: SAO RAS optical observations
- IceCube Alert 250309.32: Global MASTER-Net observations report
- EP250304A: Upper limits from Fermi-GBM Observations
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
- EP250304a: refined analysis of the EP-WXT and EP-FXT observations
- EP250302a: Mondy Continued Optical Observations
- Fermi GRB 250302A: Global MASTER-Net observations report
- Fermi GRB 250225A: Global MASTER-Net observations report
- GRB 250225B: Swift detection of a burst
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
- EP250223a: REM NIR upper limit
- GRB 250223B: Fermi GBM Final Localization
- Fermi trigger No 762020305: Global MASTER-Net observations report
- GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
- GRB 250221A: continued Mondy optical observations, brightening afterglow