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"
32796 results found.
- GRB 250621A: Fermi GBM Final Real-time Localization
- GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
- GRB250620C: Fermi GBM Observation
- GRB 250506A - SVOM/ECLAIRs Refined analysis
- GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
- GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250620C: Fermi GBM Final Real-time Localization
- GRB 250620B: Fermi GBM Final Real-time Localization
- GRB 250620A: Fermi GBM Final Real-time Localization
- GRB 250617B: Nickel telescope optical observations
- GRB 250619B: Fermi GBM Final Real-time Localization
- Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
- GRB 250615A: Kilonova-Catcher optical upper limits
- GRB 250619A: Fermi GBM Final Real-time Localization
- GRB 250617B: Assy AZT-20 Optical Observations
- GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
- Fermi GRB 250617A: Global MASTER-Net observations report
- 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: COLIBRÍ optical observations
- GRB 250617B: NOT NIR observations of the afterglow
- GRB 250617B: Swift-XRT refined Analysis
- GRB 250617B: SVOM/VT optical observation
- GRB 250617B: NUTTelA-TAO early time optical observations
- 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: SAO RAS optical observations
- GRB 250617B: Swift detection of a burst with an optical counterpart
- GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250617A: Fermi GBM Final Real-time Localization
- IPN triangulation of GRB 250612C (short/hard)
- Konus-Wind detection of GRB 250615A / EP250615a
- GRB 250615A / EP250615a: AstroSat CZTI detection
- Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
- SVOM sb25061207: AbAO AS-32 Optical Upper Limit
- GRB 250615A: COLIBRÍ optical upper limit
- GRB 250615A: DDOTI Optical Upper Limit
- GRB 250615A: Swift/UVOT Upper Limits
- Konus-Wind detection of GRB 250612C (short/hard with extended emission)
- GRB 250615A: Swift-XRT refined Analysis
- EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
- GRB 250615A: Enhanced Swift-XRT position
- Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
- GRB 250615A: Prompt enhanced Swift-XRT position
- GRB 250615A: Swift detection of a burst
- Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
- GRID detection of GRB 250612C
- Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
- GRB 250614A: Fermi GBM Final Real-time Localization
- EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
- Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
- Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
- GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
- GRB 250612B: Fermi GBM Observation
- GRB 250612C: Fermi GBM Observation
- EP250612a/GRB 250612B: JinShan optical upper limit
- GRB 250612C: SVOM/GRM observation an intermedium duration burst
- GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
- GRB 250610B: Swift-XRT refined Analysis
- GRB 250612C: Fermi GBM Final Real-time Localization
- EP250610a: Upper limit from Fermi-GBM Observations
- GRB 250612B (250612519/771424081): Fermi GBM Final Localization
- GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
- GRB 250610B: Liverpool Telescope continued monitoring
- GRB 250610B: MISTRAL/T193 and T120 OHP further observations
- GRB 250610B - SVOM/ECLAIRs refined analysis
- GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
- Fermi GBM Sub-Threshold Detection of GRB 250610B
- GRB 250610B: Swift/UVOT Detection
- GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 250610B: REM optical/NIR observations
- GRB 250610B: SVOM/VT optical shallow decay
- GRB 250610B: additional Liverpool Telescope optical observations
- GRB 250610B: SVOM/GRM analysis
- GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
- GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
- Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
- GRB 250610B: Swift-XRT counterpart detection
- GRB 250610B: SVOM/VT optical counterpart
- GRB 250610B: LT detection of the optical counterpart
- GRB 250610B: OHP/T120 optical counterpart candidate
- GRB 250610C: Fermi GBM Final Real-time Localization
- GRB 250610B: GOTO optical upper limit
- GRB 250610B : SVOM/GWAC-F60A and F50 observations
- GRB 250610B: SVOM detection of a long burst
- Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
- GRB 250610A: Fermi GBM Final Real-time Localization
- GRB 250605A: Swift-BAT refined analysis
- GRB 250609A: Fermi GBM Observation
- GRBAlpha reentry on June 9, 2025
- GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250605A: Swift/UVOT Upper Limits