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 221110A: Swift-XRT refined Analysis
- GRB 221110A: Enhanced Swift-XRT position
- GRB 221110A: VLT/X-shooter redshift
- GRB 221110A: COATLI Afterglow detection
- GRB 221110A: LCOGT Optical Afterglow Detection
- GRB 221110A: Swift detection of a burst with an optical counterpart
- Swift GRB221110.10: Global MASTER-Net OT detection
- Swift GRB221110.10: Global MASTER-Net observations report
- Fermi-GBM Observations of High Bursting Activity from SGR J1935+2154
- GRB 221009A: Hubble Space Telescope observations
- GRB 221104A: Fermi GBM Final Localization
- GRB 221108A: Fermi GBM Final Localization
- GRB 221107A: Fermi GBM Observation
- GRB 221107A: Detection by GRBAlpha
- GRB 221009A: Extended Bad Time Intervals for Fermi LAT data
- GRB 221107A: Swift/BAT-GUANO detection outside the coded FOV
- IceCube-221104A: Upper limits from a search for additional neutrino events in IceCube
- GRB 221107A: Fermi GBM Final Localization
- Correction to GCN 32852 (GRB 221009A: SARA-RM 1m Optical Afterglow Detection)
- IceCube Alert 221104.26: Global MASTER-Net observations report
- Fermi-LAT gamma-ray observations of IceCube-221104A
- IceCube-221104A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 221029A: CALET Gamma-Ray Burst Monitor detection
- High-precision position of the compact radio counterpart to GRB221009A
- GRB 221028A: GRANDMA observations
- GRB 221027B: GRANDMA observations
- GRB 221028A: Detection by VZLUSAT-2
- GRB 221029A: Fermi GBM observation
- GRB 221027C: AstroSat CZTI detection
- Konus-Wind detection of GRB 221022C
- GRB 221029A: Fermi GBM Final Localization
- GRB 221028A: Swift-XRT refined Analysis
- GRB 221028A: 1.3m DFOT Optical upper limit
- GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
- GRB 221028A: NUTTelA-TAO / BSTI Early Optical Limits
- GRB 221028A: Correction to GCN 32893 - Fluence and flux are for 50-150 keV
- GRB 221028A: AKO Optical Upper Limit
- GRB 221028A, Swift-BAT refined analysis
- GRB 221027B: Swift-BAT refined analysis
- GRB 221029A: Swift/BAT-GUANO detection outside the coded FOV
- GRB 221029A: Detection by GRBAlpha
- GRB 221028A: CrAO/ZTSh optical upper limit
- GRB 221028A: COATLI Upper Limits
- Trigger 1132968: Swift trigger is the Crab
- GRB 221028A: HCT optical upper limit
- GRB 221028A: AGILE detection
- GRB 221027A: AGILE detection
- GRB 221028A: MITSuME Okayama optical upper limits
- GRB 221028B: MAXI/GSC detection
- GRB 221028A: LCOGT Optical Upper Limits
- GRB 221027B: COATLI Upper Limits
- Swift GRB 221028A: Global MASTER-Net observations report
- GRB 221028A: BOOTES-4/MET optical upper limit
- LIGO-Virgo-KAGRA and GEO600 statement on GRB 221009A
- GRB 221028A: GIT optical upper limit
- GRB 221027B: Swift/UVOT Upper Limits
- GRB 221028A: Swift detection of a burst
- GRB 221027B: FRAM-ORM and Ondrejov SBT optical limits
- Konus-Wind detection of GRB 221017A
- Swift GRB 221027B: Global MASTER-Net observations report
- GRB 221027B: Swift-XRT refined Analysis
- GRB 221027B: BOOTES-1 optical upper limit
- GRB 221027B: Enhanced Swift-XRT position
- GRB 221027B: Swift detection of a burst
- GRB 221027A: Fermi GBM detection
- IPN triangulation of GRB 221025A (short)
- Konus-Wind detection of GRB 221022B
- GRB 221024A: Mondy optical observations
- GRB 221027A: Fermi-LAT detection
- GRB 221027A: Fermi GBM Final Real-time Localization
- GRB 221009A: Further Gemini-South Infrared Observations
- GRB 221024A: GRANDMA observations
- Fermi Gamma-ray Burst Monitor trigger 688431261/221025954 is not a GRB
- IPN triangulation of GRB 221022C (short)
- GRB 221023A: AGILE/GRID analysis
- SGR 1935+2154: AstroSat CZTI Detections
- GRB 221024A: Swift-BAT refined analysis
- GRB 221025A: AstroSat CZTI detection
- GRB 221009A: SARA-RM 1m Optical Afterglow Detection
- GRB 221025A: Fermi GBM Observation
- GRB 221009A: spectroscopic confirmation of SN in LBT spectra
- Konus-Wind detection of GRB 221023A
- GRB 221024A: Swift/UVOT UV upper limits
- GRB 221022A: Swift-XRT observations
- GRB 221024A: Swift-XRT refined Analysis
- GRB 221023A: Fermi GBM Observation
- GRB 221022B: Detection by GRBAlpha
- GRB 221025A: Fermi-LAT detection
- IPN triangulation of GRB 221022B (long)
- GRB 221024A: GIT confirmation of the optical afterglow
- LAT GRB221025.04: Global MASTER-Net observations report
- GRB 221024A: Enhanced Swift-XRT position
- GRB 221024A: D50 candidate afterglow
- GRB 221022B: AstroSat CZTI detection
- GRB 221022A: Fermi GBM detection
- GRB 221022A: Swift ToO observations
- Fermi Gamma-ray Burst Monitor detections of SGR 1935+2154
- GRB 221023A: Fermi-LAT detection
- GRB 221022B: Fermi GBM detection
- GRB 221021A: Fermi GBM observation