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').
- GRB 211107B: Swift-XRT afterglow detection
- GRB 211107A: GECAM detection
- GRB 211106A: VLT/FORS2 optical observations
- GRB 211106A, GROND observations
- GRB 211106A: Swift-XRT afterglow detection
- Fermi GRB 211109B: Global MASTER-Net observations report
- GRB 211023A: SAO RAS optical observations
- GRB 211107B: Swift-XRT observations
- MeerLICHT follow-up of GRB 211106A
- GRB 211109C: GECAM detection
- GRB 211107B: Swift ToO observations
- GRB 211109B: Fermi GBM Final Real-time Localization
- Fermi GRB 211109A: Global MASTER-Net observations report
- GRB 211109A: Fermi GBM Final Real-time Localization
- GRB 211107B: Swift/BAT detection
- GRB 211023A: A BdHN of type I
- Fermi GBM Sub-Threshold Detection of GRB 211106A
- Konus-Wind detection of GRB 211106A
- GRB 211023A: BTA spectroscopic redshift
- GRB 211107A: Fermi GBM Final Real-time Localization
- GRB 211106A: Swift-XRT observations
- GRB 211106A: Swift ToO observations
- GRB 211106A: Swift/BAT-GUANO candidate arcminute localization of a short burst
- GRB 211105A: MASTER optical inspection
- GRB 211105A: Swift/BAT-GUANO detection outside the coded FOV
- GRB 211105A: GECAM detection
- Swift Trigger 1082569 is probably not a GRB
- GRB 211105A: AGILE detection of a burst
- Fermi GBM trigger 657780594/211105201 is not a GRB
- GRB 211023A: optical detection by SBT in Ondrejov
- GRB 211023A: continued 1.3m DFOT Optical Observations and possible jet break
- Fermi trigger No 657742914: Global MASTER-Net observations report
- GRB 211104A: Fermi GBM Final Real-time Localization
- GRB 211023B: Subaru optical observation
- GRB 211024A: MITSuME Akeno optical observation
- GCN Viewer Now Available
- GRB 211102B: GECAM detection
- Fermi GRB 211102A: Global MASTER-Net observations report
- GRB 211102B: BALROG localization (Fermi Trigger 657554740 / GRB 211102587)
- GRB 211102B: Fermi GBM Final Real-time Localization
- GRB 211023B: MITSuME Akeno optical upper limits
- GRB 211102A: BALROG localization (Fermi Trigger 657533168 / GRB 211102338)
- GRB 211102A: Fermi GBM Final Real-time Localization
- GRB 211024B: Optical afterglow observation by Ondrejov D50
- GRB 211024A: 1.3m DFOT observations
- Fermi GRB 211031A: Global MASTER-Net observations report
- GRB 211031A: Fermi GBM Final Real-time Localization
- IPN triangulation of GRB 211022A
- GRB 211023A: 1.3m DFOT Optical Observations
- Konus-Wind detection of GRB 211023A
- GRB 2121023B: 6 GHz VLA radio upper limit
- GRB 211023A: Terskol optical observations
- AMON NuEm-211020A: No Candidate Counterparts from Swift-XRT follow up observations
- GRB 211023A: continued Mondy optical observations
- GRB 211024A: Swift-XRT source 4 is not an afterglow.
- GRB 211023B: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
- Fermi GRB 211027A: Global MASTER-Net observations report
- GRB 211024A: Possible afterglow candidate from GIT
- GRB 211024A: Swift-XRT observations
- GRB 211027A: Fermi GBM Final Real-time Localization
- GRB 211024A: Fermi GBM detection
- GRB 211018A: Swift-XRT observations
- GRB 211025A: Optical Afterglow Detection
- GRB211023A: optical afterglow detection from Konkoly Observatory
- GRB 211024A: Swift ToO observations
- GRB 211024A: Swift/BAT-GUANO detection and candidate arcminute localization of a short burst
- GRB 211024B: Swift/UVOT detection
- GRB 211023A: Mondy optical observations
- GRB 211023B: Mondy optical afterglow confirmation
- GRB 211023B: Gemini-North Optical Observations
- Swift GRB 211025A: Global MASTER-Net observations report
- GRB 211023B: LDT Optical Afterglow Detection
- IceCube-211023A: Upper limits from a search for additional neutrino events in IceCube
- Correction to GCN 30965: GRB 211023A: Fermi GBM detection
- GRB 211025A: Swift-BAT refined analysis
- GRB 211025A: Swift-XRT refined Analysis
- GRB 211024B: CAHA 2.2m Detection; ultra-long GRB?
- GRB 211024B: Swift-XRT refined Analysis
- IPN Triangulation of GRB 211019A
- Possible Short GRB 211023B: CAHA 2.2m Detection
- GRB 211025A: Swift/UVOT Detection
- GRB 211023A: 1.5m OSN optical observation
- GRB 211024B: Swift-BAT refined analysis
- GRB 210610B: Sintesz-Newton/CrAO optical observations
- GRB 211025A: Enhanced Swift-XRT position
- GRB 211025A: Swift detection of a burst
- GECAM detection of a short burst probably from SGR J1555.2-5402
- GRB 211024B: Nanshan/NEXT optical afterglow detection
- GRB 210919A: FORS2/VLT observations
- GRB 211023A: OAJ Bright Afterglow Confirmation
- Swift GRB 211024B: Global MASTER-Net observations report
- GRB 211024B: Swift detection of a burst
- GRB 211023B: Swift-BAT refined analysis
- Fermi-LAT Gamma-ray Observations of IceCube-211023A
- GRB 211023A: MASTER OT J045237.07+851925.2 - optical counterpart discovery
- GRB 211023B: BOOTES-4/MET and 1.5m OSN optical upper limit
- GRB 211023B: Swift/UVOT Detection
- GRB 211024A: GECAM detection
- GRB 211023B: RATIR Optical and NIR Upper Limits
- GRB 211023B: TSHAO optical observation