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"- Konus-Wind detection of the second intermediate flare from SGR 1935+2154
- IPN triangulation of a bright burst from SGR 1935+2154
- Fermi trigger No 652957973: Global MASTER-Net observations report
- Fermi trigger No 652944960: Global MASTER-Net observations report
- Fermi trigger No 652981861: Global MASTER-Net observations report
- GRB 210826A: further Swift-XRT observations
- GRB 210909B: GECAM detection
- GECAM observations of a series of bursts from SGR J1935+2154
- Swift detection of a burst from SGR Swift J1555.2-5402
- Fermi trigger No 652934203: Global MASTER-Net observations report
- GECAM observation of a burst from SGR J1935+2154
- GECAM observation of a burst from SGR J1935+2154
- Fermi trigger No 652927551: Global MASTER-Net observations report
- GRB 210619B: Maidanak and Assy optical observations, broken power law parametrization
- Fermi trigger No 652911693: Global MASTER-Net observations report
- Fermi trigger No 652906639: Global MASTER-Net observations report
- Fermi GRB 210909A: Global MASTER-Net observations report
- GECAM observation of a burst from SGR J1555.2-5402
- GRB 210909A: Fermi GBM Final Real-time Localization
- GRB 210905A: Swift/UVOT Upper Limits
- GRB 210905A: ATCA detection
- GRB 210905A: ALMA detection
- GRB 210905A: AstroSat CZTI detection
- GRB 210905A, GROND observations
- Konus-Wind detection of GRB 210905A
- Fermi GBM Sub-Threshold Detection of GRB 210905A
- Fermi GBM trigger 652585475 / 210906073 is not a GRB
- Fermi trigger No 652585475: Global MASTER-Net observations report
- GRB 210905A: Swift-XRT refined Analysis
- GRB 210610A: Maidanak and AbAO optical observations
- GRB 210827B: GECAM detection
- GRB 210905A: DECam Detection
- GRB 210905A: REM NIR afterglow detection
- GRB 210905A: VLT/X-shooter spectroscopic redshift
- GRB 210905A: Continued LCO Optical Observations
- GRB 210905A: LCO Optical Detection
- GRB 210905A: Enhanced Swift-XRT position
- GRB 210901A: Swift/UVOT Upper Limits
- Swift GRB 210905A: Global MASTER-Net observations report
- GRB 210905A: Swift detection of a burst
- Fermi GRB 210904A: Global MASTER-Net observations report
- GRB 210904A: Fermi GBM Final Real-time Localization
- Swift GRB210903.59: Global MASTER-Net observations report
- Swift GRB210903.58: Global MASTER-Net observations report
- Swift GRB210903.58: Global MASTER-Net observations report
- Fermi GRB 210903A: Global MASTER-Net observations report
- GRB 210903C: Fermi GBM Final Real-time Localization
- GRB 210820A: TSHAO optical upper limit
- Fermi GRB 210903B: Global MASTER-Net observations report
- GRB 210901A: GROND observations
- GRB 210903B: Fermi GBM Final Localization
- Fermi GBM observation of a burst from SGR J1555.2-5402
- GRB 210903A: Fermi GBM Final Real-time Localization
- GRB 210901A: Swift-XRT refined Analysis
- GRB 210901A: Swift-BAT refined analysis
- GRB 210901A: Enhanced Swift-XRT position
- GRB 210901A: LCO Optical Upper Limit
- Swift GRB 210901A: Global MASTER-Net observations report
- GRB 210901A: Swift detection of a burst
- GRB 210827A: further Swift-XRT observations
- GRB 210822A: CALET Gamma-Ray Burst Monitor detection
- GRB 210827A: Swift/UVOT Upper Limits
- GRB 210827A: BOOTES-5/JGT optical upper limit
- Integral GRB210829.17: Global MASTER-Net observations report
- IBAS Alert n. 9366 not a GRB
- Integral GRB210829.14: Global MASTER-Net observations report
- GRB 210827A: Fermi GBM Observation
- GRB 210826A: AstroSat CZTI detection
- Fermi GRB 210827A: Global MASTER-Net observations report
- Fermi GRB 210827B: Global MASTER-Net observations report
- GRB 210827A: Swift-XRT observations
- GRB 210827A: Swift ToO observations
- GRB 210827A: Swift/BAT-GUANO detection and arcminute localization
- GRB 210820A: CAHA 2.2m Optical Detection
- GRB 210824A: Swift/UVOT Upper Limits
- GRB 210826A: Swift/UVOT Upper Limits
- POLAR detection of a SGR-like burst
- GRB 210827B: BALROG localization (Fermi Trigger 651751821 / GRB 210827424)
- GRB 210827B: Fermi GBM Final Real-time Localization
- GRB 210826A: Swift-XRT observations
- GRB 210827A: Fermi GBM Final Real-time Localization
- GRB 210822A: CAHA 2.2m observations
- GRB 210824A: Swift-BAT refined analysis
- GRB 210826A: Fermi-LAT detection
- Fermi GRB 210826A: Global MASTER-Net observations report
- GRB 210826A: Tiled Swift observations
- GRB 210824A: MITSuME Akeno optical upper limits
- GRB 210826A: BALROG localization (Fermi Trigger 651654110 / GRB 210826293)
- GRB 210826A: Fermi GBM Final Real-time Localization
- Swift GRB210825.29: Global MASTER-Net observations report
- GRB 210822A: TSHAO continued optical observation
- GRB 210822A: VLA detection
- GRB 210822A: TSHAO optical observation
- Swift detection of an outburst from SGR Swift J1555.2-5402
- GRB 210822A: Swift/UVOT Detection
- Swift GRB 210824A: Global MASTER-Net observations report
- GRB 210824A: BOOTES-5/JGT optical upper limit
- GRB 210824A: Fermi GBM Observation
- Fermi GRB 210824A: Global MASTER-Net observations report
- GRB 210824A: Nanshan/NEXT optical upper limit