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.
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"19353 results found.
- GRB 250625A: GECAM-B detection
- GRB 250625A: Swift/UVOT Upper Limits
- GRB 250625A: ABObservatory afterglow detection
- GRB 250625A: COLIBRÍ optical observations
- GRB 250625A: Fermi-LAT detection
- GRB 250625A: Swift-XRT refined Analysis
- GRB 250625A: JinShan optical observations
- GRB250625A: Fermi GBM Observation
- Swift GRB 250625A: Global MASTER-Net observations report
- GRB 250625A: SVOM/VT optical confirmation
- GRB 250620B: Fermi GBM Observation
- GRB 250625A: Enhanced Swift-XRT position
- GRB 250625A: Swift detection of a burst
- GRB 250620A: AstroSat CZTI detection
- GRB 241018A: Maidanak optical observations
- GRB 250617B: Swift-BAT refined analysis
- IPN triangulation of GRB 250620С (long/bright)
- GRB 250620A: SVOM/GRM observation of a short burst
- GRB250620A: Fermi GBM Observation
- GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- GRB 250619B: Fermi GBM Observation
- GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
- GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250615A: Kilonova-Catcher optical upper limits
- GRB 250617B: Assy AZT-20 Optical Observations
- GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
- GRB 250615A/EP250615a: FTW optical and NIR observations
- sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
- GRB 250617B: Swift/UVOT Detection
- GRB 250617B: Kilonova-Catcher optical afterglow detection
- GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
- GRB 250617B: NOT NIR observations of the afterglow
- GRB 250617B: Swift-XRT refined Analysis
- GRB 250617B: SVOM/VT optical observation
- Swift GRB 250617B: Global MASTER-Net observations report
- GRB 250617B: GOTO optical upper limit
- GRB 250617B: Enhanced Swift-XRT position
- GRB 250617B: Fermi GBM Observation
- GRB 250615A: Swift-BAT refined analysis
- GRB 250617B: Fermi GBM Final Localization
- GRB 250617B: Ondrejov D50 optical afterglow detection
- GRB 250617B: Swift detection of a burst with an optical counterpart
- GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- EP#01709178975: Swift-XRT counterpart detection
- Konus-Wind detection of GRB 250615A / EP250615a
- GRB 250615A / EP250615a: AstroSat CZTI detection
- GRB 250615A: COLIBRÍ optical upper limit
- GRB 250615A: DDOTI Optical Upper Limit
- GRB 250615A: Swift/UVOT Upper Limits
- GRB 250615A: Swift-XRT refined Analysis
- GRB 250615A: Enhanced Swift-XRT position
- GRB 250615A: Prompt enhanced Swift-XRT position
- GRB 250615A: Swift detection of a burst
- Swift GRB 250615A: Global MASTER-Net observations report
- sb25061207: Mephisto optical upper limits
- sb25061218: Swift-XRT observations
- sb25061207: EP-FXT follow-up observation and afterglow candidate
- sb25061207: Swift-XRT observations
- GRB 250610B: Swift-XRT refined Analysis
- EP250610a: continuous follow-up observations with EP-FXT
- GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
- Swift GRB250612.04: Global MASTER-Net observations report
- GRB 250610B: Swift/UVOT Detection
- EP250610A: Swift/UVOT Upper limits
- GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
- GRB 250610B: Swift-XRT counterpart detection
- GRB 250610B: SVOM/VT optical counterpart
- EP250610a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250605A: Swift-BAT refined analysis
- EP250610a: SVOM/VT optical upper limit
- EP250610a: REM optical/NIR observations
- GRB 250609A: Fermi GBM Observation
- EP250610a: Swift-XRT counterpart detection
- GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250605A: Swift/UVOT Upper Limits
- GRB 250527C: CrAO Optical Upper Limit
- GRB 250605A: SVOM/VT optical upper limit
- GRB 250605A: Swift-XRT refined Analysis
- GRB 250605A: Enhanced Swift-XRT position
- GRB 250605A: LT optical observations
- GRB 250605A: Swift detection of a burst
- Swift GRB250605.79: Global MASTER-Net observations report
- Konus-Wind detection of GRB 250601A
- IPN triangulation of GRB 250404B
- IPN triangulation of GRB 250529A
- GRB 250601A: PRIME H band upper limit.
- GRB 250601A: PRIME J band upper limit.
- GRB 250601A: VLT/FORS2 Optical Observation
- GRB 250601A: Fermi GBM Observation
- GRB 250603A: Swift/UVOT Upper Limits
- GRB 250603A: Swift-XRT refined Analysis
- GRB 250603A: Enhanced Swift-XRT position
- GRB 250603A: Swift-XRT position and confirmation of GRB nature
- Swift GRB250603.05: Global MASTER-Net observations report
- GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
- GRB 250530C: Swift-BAT refined analysis
- GRB 250601A: EP-FXT follow-up observation and afterglow candidates
- GRB 250601A: Swift/XRT candidate afterglow
- GRB 250601A: Swift-XRT observations