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').
- Fermi-LAT Gamma-ray Observations of IceCube-210730A
- Trigger 1062273: Swift detection of 4U 1700-377
- GRB 210730A: Campo Imperatore optical observations
- GRB 210730A: BOOTES-5/JGT and 2.2m CAHA telescopes optical limit
- Swift GRB 210730A: Global MASTER-Net observations report
- Fermi trigger No 649390368: Global MASTER-Net observations report
- GRB 210730A: TNG optical observations
- IceCube-210730A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 210726A: Chandra detection of the X-ray afterglow
- GRB 210730A: Fermi GBM observation
- Fermi trigger No 649313854: Global MASTER-Net observations report
- GRB 210730A: AstroSat CZTI detection
- GRB 210730A: Swift-BAT refined analysis
- GRB 210730A: Swift-XRT refined Analysis
- GRB 210730A: Swift/UVOT Upper Limits
- GRB 210724A: Early CAHA 2.2m limit
- GRB 210730A: Enhanced Swift-XRT position
- GRB 210727A: AstroSat CZTI detection
- GRB 210730A: Swift detection of a burst near M82
- GRB 210724A: Corrected Swift-XRT enhanced position
- Fermi GBM Sub-Threshold Detection of GRB 210725B
- GRB 210726A: OSIRIS/GTC observations
- GRB 210727A: CALET Gamma-Ray Burst Monitor detection
- GRB 210726A: Deep CAHA 2.2m limit
- GRB 210726A: 6 GHz VLA radio upper limit
- IPN triangulation of GRB 210727A (short)
- Fermi GBM Sub-Threshold Detection of GRB 210726A
- GRB 210714A: Fermi GBM observation
- GRB 210702A: MeerKAT radio detection
- GRB 210726A: Swift-XRT refined Analysis
- GRB 210726A: Swift-BAT refined analysis
- GRB 210726A: Likely a short burst
- GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy
- GRB 210727A: AGILE/MCAL detection
- Fermi trigger No 649072251: Global MASTER-Net observations report
- GRB 210727A: BALROG localization (Fermi Trigger 649072251 / GRB 210727410)
- GRB 210725A: AbAO optical upper limit
- GRB 210724A: Swift/UVOT Upper Limits
- GRB 210723A: Swift/UVOT Upper Limits
- GRB 210725A: Swift/UVOT Upper Limits
- GRB 210725B: Swift/UVOT Upper Limits
- GRB 210726A: CAHA 2.2m telescope optical limit
- GRB 210726A: Enhanced Swift-XRT position
- GRB 210726A: Swift detection of a burst
- Swift GRB210726.80: Global MASTER-Net observations report
- Fermi trigger No 648959581: Global MASTER-Net observations report
- GRB 210725B: Swift-XRT refined Analysis
- GRB 210725A: Fermi GBM detection
- GRB 210724A: Zeiss-1000 of Koshka observatory, optical upper limit
- GRB 210725A: Swift-XRT refined Analysis
- GRB 210725B: Swift-BAT refined analysis
- GRB 210724A: Swift-XRT refined Analysis
- GRB 210725A: Swift-BAT refined analysis
- GRB 210724A: Swift-BAT refined analysis
- Swift GRB 210725B: Global MASTER-Net observations report
- GRB 210724A: Afterglow candidate from OSIRIS/GTC
- GRB 210725B: Enhanced Swift-XRT position
- GRB 210725A: MITSuME Akeno optical upper limits
- GRB 210725B: Swift detection of a burst
- GRB 210725A: CALET Gamma-Ray Burst Monitor detection
- GRB 210723A: CALET Gamma-Ray Burst Monitor detection
- GRB 210722A: continued Assy optical observations
- GRB 210722A: Nanshan/NEXT further optical observations
- GRB 210725A: KAIT Optical Upper Limit
- Fermi trigger No 648868114: Global MASTER-Net observations report
- GRB 210725A: Swift detection of a burst
- Swift GRB210725.16: Global MASTER-Net observations report
- GRB 210723A: Fermi GBM Observation
- GRB210724A: MeerLICHT upper limits
- GRB 210724A: Swift detection of a burst
- Swift GRB210724.84: Global MASTER-Net observations report
- GRB 210723A: Swift-BAT refined analysis
- GRB 210722A: continued Assy optical observations
- GRB 210723A: Swift-XRT refined Analysis
- GRB 210722A: D50 optical detection
- Swift GRB 210723A: Global MASTER-Net observations report
- GRB 210722A: Fermi GBM observation
- GRB 210722A: Swift-BAT refined analysis
- GRB 210722A: Kitab optical observations, light curve
- GRB 210722A: Redshift from OSIRIS/GTC
- GRB 210723A: Prompt enhanced Swift-XRT position
- GRB 210723A: Swift detection of a burst
- GRB 210722A: RATIR Optical Observations
- GRB 210722A: Swift-XRT refined Analysis
- GRB 210722A: Swift/UVOT Detection
- GRB 210722A: GIT optical detection and preliminary analysis
- Swift GRB 210722A: Global MASTER-Net observations report
- GRB 210702A: ALMA detection of mm-band rebrightening
- GRB 210722A: Assy optical detection
- GRB 210702A: ATCA detection of radio rebrightening
- GRB 210722A: Nanshan/NEXT optical afterglow observations
- GRB 210722A: Swift detection of a burst with a bright optical counterpart
- Fermi trigger No 648602917: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-210717A
- GRB 210719A: GECAM detection
- IceCube-210717A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
- Fermi trigger No 648359752: Global MASTER-Net observations report
- Fermi trigger No 648278666: Global MASTER-Net observations report
- IceCube-210717A: IceCube observation of a high-energy neutrino candidate track-like event
- Konus-Wind detection of GRB 210714A