GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"- GRB 250407A: Fermi GBM Final Real-time Localization
- IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- IceCube 250406.951: DDOTI Optical Observations
- GRB 250406A: AstroSat CZTI detection
- IceCube Alert 250406.95: Global MASTER-Net observations report
- Fermi trigger No 765663719: Global MASTER-Net observations report
- EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
- Fermi GRB 250406A: Global MASTER-Net observations report
- GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- GRB 250406A: Fermi GBM Final Real-time Localization
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- Fermi trigger No 765619921: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
- GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
- GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
- EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
- Konus-Wind detection of GRB 250404A / EP250404a
- GRB 250404A / EP250404a: Mondy optical observations
- EP250404a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
- EP250402a: Optical upper limit with PD 1.3m observations
- GRB 250404A / EP250404a: NOT optical observations
- GRB 250331D: Swift-XRT afterglow detection
- GRB 250404B: AstroSat CZTI detection of a short burst
- GRB 250403A: AstroSat CZTI detection
- EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
- EP250404a: REM optical/NIR observations
- EP250404a: Seimei/TriCCS optical counterpart detection
- EP250404A: COLIBRÍ/DDRAGO Optical Observations
- EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
- EP250404a: LCO optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- GRB 250403A: Montarrenti Observatory optical detection
- GRB 250404A: Fermi GBM Detection
- EP250404a: Global MASTER-Net observations report
- GRB 250403A: KAIT optical observations
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- EP250404a: Xinglong-2.16m spectroscopic redshift
- GRB 250403A: Fermi GBM observations
- GRB 250327B: VIRT Optical Upper Limit
- EP250404a: Mephisto multi-band optical detection
- GRB 250331C Swift-BAT refined analysis
- GRB 250331B Swift-BAT refined analysis
- GRB 250330A Swift-BAT refined analysis
- EP250321A: J band upper limit by SYSU 80cm telescope
- EP250404a: BOOTES-4/JGT optical afterglow detection
- EP250404a: Nanshan/HMT optical counterpart detection
- EP250404a: Einstein Probe detection of an X-ray transient
- GRB 250404A: Fermi GBM Final Real-time Localization
- GRB 250402A: Mondy optical observations
- GRB 250403A: Swift/UVOT Detection
- GRB 250402A: Swift/UVOT Upper Limits
- EP250402a: Optical upper limit with Kinder observations
- GRB 250403A: SVOM/VT optical observation
- GRB 250403A: REM NIR afterglow detection
- GRB 250403A: LCO optical counterpart detection
- IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
- GRB 250403A: JinShan optical observations
- GRB 250402A: EP-FXT afterglow detection
- GRB 250403A: Optical counterpart detection by LCO.
- EP250402a: EP-FXT follow-up observations
- GRB 250403A: Swift-XRT observations
- GRB 250322A: 10 GHz VLA radio upper limits
- Fermi GRB 250403A: Global MASTER-Net observations report
- GRB 250403A: GOTO optical counterpart follow-up observations
- GRB 250402A: NUTTelA-TAO Early Optical Limits
- GRB 250403A: GMG Optical Observation
- GRB 250403A: 1.6m Mephisto multi-band optical detection
- GRB 250402A: Fermi GBM Observation
- GRB 250403A: SVOM/C-GFT optical observations
- GRB 250403A: GOTO detection of the optical afterglow
- GRB 250402A: Swift-XRT observations
- GRB 250403A : SVOM detection of a burst
- GRB 250403A: Fermi GBM Final Real-time Localization
- GRB 250225B: VLT host galaxy redshift z = 0.950
- GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
- GRB 250402A: REM optical/NIR upper limits
- GRB 250402A: LCO optical counterpart detection
- GRB 250402A: refined SVOM/MXT data analysis
- The EP-WXT trigger 01709133862 is a flaring star
- EP250402a: Einstein Probe detection of a fast X-ray transient
- GRB 250402B: AstroSat CZTI detection of a short burst
- GRB 250402A: SVOM/VT optical counterpart
- GRB 250402A: SVOM detection of a burst
- GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250314A: ALMA detection
- GRB 250329B: Swift/UVOT Upper Limit
- GRB 250329A: Swift/UVOT Upper Limit
- GRB 250327B: Swift/UVOT Detection
- GRB 250327A: Swift/UVOT Upper Limits
- GRB 250331E: SVOM/GRM observation
- GRB 250327B: Kilonova-Catcher Observations
- GRB250331D: AbAO optical observations