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"- GRB 210411C: ePESSTO+ NTT optical observations
- GRB 210411C: Swift-XRT refined Analysis
- GRB 210411C: VLT/X-shooter redshift
- GRB 210410A: MITSuME Akeno optical upper limits
- Swift GRB 210411C: Global MASTER-Net observations report
- GRB 210411C: BOOTES-4/MET optical upper limit
- GRB 210411C: LCO Optical Afterglow Candidate
- Fermi GRB 210411B: Global MASTER-Net observations report
- GRB 210411C: Enhanced Swift-XRT position
- GRB 210406A: 10.4m GTC follow-up observation
- GRB 210410A: AGILE/MCAL analysis
- Konus-Wind detection of GRB 210410A
- GRB 210411D: BALROG localization (Fermi Trigger 639851475 / GRB 210411688)
- GRB 210411D: Fermi GBM Final Real-time Localization
- GRB 210411C: Swift detection of a burst with an optical counterpart
- GRB 210410A: Swift-BAT refined analysis
- GRB 210411B: Fermi GBM Final Real-time Localization
- Fermi GRB 210411A: Global MASTER-Net observations report
- GRB 210410A: Swift-XRT refined Analysis
- GRB 210411A: Fermi GBM Final Real-time Localization
- GRB 210410A: Fermi GBM detection
- GRB 210410A: Swift/UVOT Upper Limits
- GRB210410A: Joint inspection of RATIR and D50 data
- GRB 210406A: Swift-XRT observations
- GRB 210410A: RATIR Optical and NIR Observations
- GRB 210409A: GECAM detection
- GRB 210410A: AGILE detection of a burst
- GRB 210410A: Fermi-LAT detection
- GRB210410A: Candidate optical afterglow by Ondrejov D50
- Fermi GRB 210410A: Global MASTER-Net observations report
- GRB 210410A: Swift XRT localization
- GRB 210410A: Fermi GBM Final Real-time Localization
- Swift Triggers 1042031 and 1042032 are not astrophysical events
- GRB 210406A: Mondy optical afterglow candidate
- GRB 210406A: Swift ToO observations
- GRB 210406B: Fermi GBM detection
- Konus-Wind detection of GRB 210406A
- GRB 210406A: Fermi GBM detection
- GRB 210406A: Mondy optical upper limit
- GRB 210406A: Konkoly Obs. optical upper limit
- GRB 210406A: BOOTES-4/MET optical upper limit
- GRB 210406A: A long GRB detected by INTEGRAL
- Integral GRB210406.72: Global MASTER-Net observations report
- GRB 210402A: MASTER prompt and follow up optical observation
- GRB 210402A: Swift/UVOT Upper Limits
- GRB 210402A: Fermi GBM detection
- GRB 210402A: Further NOT optical observations
- GRB 210402A: Swift-BAT refined analysis
- GRB 210404.141: DDOTI Upper Limits
- GRB 210207B: Prompt and very late time observations with HCT.
- GRB 210401A: GECAM detection
- GRB 210402A: NOT optical afterglow candidate
- Fermi trigger No 639199407: Global MASTER-Net observations report
- GRB 210402A: BOOTES-network early optical upper limit
- GRB 210403A: Swift-BAT refined analysis
- GRB 210402A: LBT observations
- GRB 210402A: DDOTI Upper Limits
- Swift GRB210403.35: Global MASTER-Net observations report
- GRB 210402A: Swift-XRT refined Analysis
- GRB 210330A: AstroSat CZTI detection
- GRB 210403A: Swift detection of a burst
- GRB 210402A: Montarrenti Observatory upper limit
- GRB 210328A: AstroSat CZTI detection
- GRB 210402A: NOT optical upper limits
- Konus-Wind detection of GRB 210401A
- GRB 210402A: Swift detection of a burst
- Fermi trigger No 639093861: Global MASTER-Net observations report
- Swift GRB210402.92: Global MASTER-Net observations report
- Fermi GRB 210401A: Global MASTER-Net observations report
- GRB 210401A: Fermi GBM Final Real-time Localization
- GRB 210330A: MASTER optical observation
- GRB 210328A: GECAM detection
- GRB 210330A: GECAM detection
- GRB 210324A: AstroSat CZTI detection
- GRB 210324C: AstroSat CZTI detection
- GRB 210328A: BALROG localization (Fermi Trigger / GRB 210328865)
- GRB 210328A: Fermi GBM Final Real-time Localization
- GRB 210326A: Insight-HXMT/HE detection
- GRB 210326A: Fermi GBM Final Localization
- Fermi trigger No 638414549: Global MASTER-Net observations report
- Konus-Wind detection of GRB 210324C
- IPN triangulation of GRB 210324C
- GRB 210323A: Insight-HXMT/HE detection
- GRB 210321A: OSN Upper Limit
- GRB 210323A: MASTER optical observation
- Fermi GRB 210324C: Global MASTER-Net observations report
- Fermi GRB 210324B: Global MASTER-Net observations report
- GRB 210323A: Swift-BAT refined analysis
- GRB 210323A: Gemini-North Optical Source Detection
- GRB 210324C: BALROG localization (Fermi Trigger 638308803 / GRB 210324833)
- GRB 210324C: Fermi GBM Final Real-time Localization
- Short GRB 210323A: GTC Observations
- GRB 210312B: OSN Afterglow Observations
- GRB 210324B: Fermi GBM Final Real-time Localization
- GRB 210323B: Swift ToO observations
- Konus-Wind detection of GRB 210323A (short)
- GRB 210323A: Swift/UVOT Upper Limits
- GRB 210323A: Classification and redshift estimation
- GRB 210323A: Kitab optical upper limit
- GRB 210323A: Fermi GBM detection