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 201103B: AGILE detection
- GRB 201104A: Fermi GBM observation
- GRB 201104A: AGILE/MCAL detection
- GRB 201104A: Fermi-LAT detection
- GRB 201104B: Swift/UVOT Detection
- GRB 201104B: MASTER optical observation
- GRB 201104B: Swift detection of a burst
- Fermi GRB 201104A: Global MASTER-Net observations report
- GRB 201104A: Fermi GBM Final Real-time Localization
- GRB 201015A: Late X-ray Detections with Chandra
- Fermi GRB 201103A: Global MASTER-Net observations report
- GRB 201103A: Fermi GBM Final Real-time Localization
- Swift GRB 201031A: Global MASTER-Net observations report
- Swift Trigger 1003313 (a.k.a. GRB 201031A) is not an astrophysical event
- Fermi GRB 201031B: Global MASTER-Net observations report
- GRB 201031B: BALROG localization (Fermi Trigger 625859489 / GRB 201031744)
- GRB 201031B: Fermi GBM Final Real-time Localization
- GRB 201031A: Swift detection of a burst
- GRB 201029A: Swift-BAT refined analysis
- IceCube 201021A: Swift follow-up of Fermi J1725.5+1312
- Swift GRB 201029A: Global MASTER-Net observations report
- GRB 201029A: Swift/UVOT Upper Limits
- GRB 201029A: Fermi GBM detection
- GRB 201029A: Swift-XRT refined Analysis
- GRB 201029A: BOOTES-1 optical upper limit
- GRB 201029A: Enhanced Swift-XRT position
- GRB 201029A: FRAM-ORM optical limit
- Fermi trigger No 625695596: Global MASTER-Net observations report
- GRB 201029A: Swift detection of a burst
- GRB 201027A: MITSuME Akeno optical upper limits
- GRB 201027A: Swift-BAT refined analysis
- GRB 201026A: Swift-BAT refined analysis
- GRB 201027A: Swift/UVOT Upper Limits
- GRB 201027A: Swift-XRT refined Analysis
- GRB 201026A: Fermi GBM detection
- GRB 201026A: Swift-XRT refined Analysis
- Baksan Neutrino Observatory Alert 201027.41: Global MASTER-Net observations report
- GRB 201027A: 1.5m OSN optical upper limit
- GRB 201026A: Swift/UVOT Upper Limits
- GRB 201027A: Enhanced Swift-XRT position
- GRB 201026A: Enhanced Swift-XRT position
- GRB 201026A: FRAM-ORM optical detection limit
- GRB 201020A: 1.3m DFOT, optical upper limits
- GRB 201027A: Swift detection of a burst
- Swift GRB201027.05: Global MASTER-Net observations report
- GRB 201026A: NanShan/NEXT-0.6m optical upper limit
- GRB 201026A: NOT optical upper limits
- GRB 201026A: Swift detection of a burst
- Swift GRB201026.94: Global MASTER-Net observations report
- GRB 201024A: 1.3m DFOT optical observations
- GRB 201020B: 1.3m DFOT continued optical follow-up observations
- GRB201024A: correction to GCN28777 - there was no rebrightening
- GRB 201024A: MITSuME Akeno optical upper limits
- GRB 201024A: Swift-BAT refined analysis
- GRB201024A: rebrightening after initial steep decline
- GRB 201020B: HCT and GIT continued optical follow-up observations
- GRB 201024A: Swift-XRT refined Analysis
- GRB 201024A: Swift/UVOT Detection
- GRB 201020B: follow-up observations with Savelli Telescope
- GRB 201020B: 1.3m DFOT optical observations
- GRB 201024A: VIRT optical observations
- GRB 201024A: Enhanced Swift-XRT position
- GRB 201020B: follow-up observations at Konkoly
- GRB 201020B: continued Mondy optical observations
- GRB 200901A: FRAM-Auger optical limit
- GRB 201024A: FRAM-ORM afterglow detection
- GRB 201020B: Redshift from GTC/OSIRIS
- GRB 201024A: Redshift from GTC/OSIRIS
- GRB 201024A: BOOTES-2/TELMA early optical observation and 1.5m OSN follow-up
- GRB 201024A: MASTER correction to GCN 28760
- GRB 201024A: Swift detection of a burst with an optical afterglow
- Swift GRB201024A: Global MASTER-Net OT detection
- Swift GRB201024.12: Global MASTER-Net observations report
- IceCube-201021A: No significant detection in HAWC
- IceCube-201021A: One candidate counterpart from the Zwicky Transient Facility
- IceCube-201021A: Optical counterpart of WISEA J172314.13+142101.5
- GRB 201021C: Swift-BAT refined analysis
- GRB 201021C: Swift-XRT refined Analysis
- GRB 201020B: GROWTH-India Telescope optical observations
- Baksan Neutrino Observatory Alert 201022.66: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-201021A and detection of a new gamma-ray source, Fermi J1725.5+1312
- GRB 201020B: Konkoly Obs. optical detection
- Swift-XRT observations of IceCube 201021A (2)
- GRB 201021C: Fermi GBM detection
- GRB 201020A: GROWTH-India Telescope late-time optical upper limit
- IceCube-201021A: Upper limits from a search for additional neutrino events in IceCube
- GRB 201021C: Swift/UVOT Detection
- Konus-Wind detection of GRB 201020A
- GRB 201020B: Swift/UVOT Detection
- GRB 201020A: Swift/UVOT Observations
- GRB 201014A: 2.0m HCT upper limit
- GRB 201020B: Swift-XRT afterglow detection
- GRB 201021C: VLT/X-shooter redshift
- IceCube-201021A: No neutrino counterpart candidates in ANTARES search
- GRB 201020A: VIRT optical observations
- GRB 201021C: Enhanced Swift-XRT position
- IceCube-201021A: Upper limits from Fermi-GBM Observations
- HAWC-201019A: not observable by Fermi-GBM
- GRB 201021C: MASTER optical synchronously observation
- IceCube-201021A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation