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 220101A: OASDG optical observations
- GRB 220101A : Eiso equals the maximum isotropic GRB energy
- GRB 220101A: GMG observation
- GRB 220101A: Asiago spectroscopic and photometric detection
- Fermi trigger No 662768315: Global MASTER-Net observations report
- GRB220101A: optical afterglow detection from Konkoly Observatory
- GRB 220101A: Fermi GBM Detection
- GRB 220101A: NOT redshift confirmation
- GRB 220101A: CAHA 2.2m/CAFOS detection
- GRB 220101A: Liverpool telescope imaging of a high-redshift afterglow
- GRB 220101A: THO optical observations
- GRB 220101A: Swift-XRT refined Analysis
- GRB 220101A: AGILE detection
- GRB 220101A: Xinglong-2.16m photometry and spectroscopy
- Swift GRB220101.22: Global MASTER-Net observations report
- GRB 220101: Swift/UVOT Detection
- GRB 220101A: Fermi-LAT detection
- GRB 220101A: Enhanced Swift-XRT position
- GRB 220101A: Correction to GCN 31347
- GRB 220101A: Swift detection of a burst with a bright optical counterpart
- IPN triangulation of GRB 211219A
- GRB 211231A: GECAM detection
- GRB 211229B: AGILE detection
- GRB 211231A: Fermi GBM Final Real-time Localization
- GRB 211229A: Swift-XRT and UVOT observations
- GRB 211227A: Deep early CAHA 2.2m/CAFOS observation
- GRB 211229A: Fermi GBM observation
- GRB 211229B: GECAM detection
- GRB 211229C: Swift/BAT-GUANO detection likely outside the coded FOV
- Fermi GRB 211229B: Global MASTER-Net observations report
- GRB 211229B: Fermi GBM Final Real-time Localization
- GRB 211229A: Swift ToO observations
- GRB 211229A: Swift/BAT-GUANO arcminute localization
- GRB 211227A: CALET Gamma-Ray Burst Monitor detection
- GRB 211225B: CALET Gamma-Ray Burst Monitor detection
- GRB 211229A: GECAM detection
- Fermi GRB 211229A: Global MASTER-Net observations report
- GRB 211229A: Fermi GBM Final Real-time Localization
- GRB 211227A: Swift/UVOT Upper Limits
- GRB 211227A: Swift-XRT refined Analysis
- GRB 211227A: Swift-BAT refined analysis
- Konus-Wind detection of the intermediate flare from SGR 1935+2154
- GRB 211227A: A possible short GRB with extended emission at z = 0.228?
- GRB 211227A: Liverpool Telescope upper limits
- GRB 211227A: Enhanced Swift-XRT position
- GRB 211227A: LCO Optical Observations
- GRB 211227A: Nanshan/NEXT optical observations and host galaxy candidate
- GRB 211227A: MAXI/GSC detection
- GRB 211227A: BOOTES-2/TELMA optical upper limit
- GRB 211221A: Swift/UVOT Upper Limits
- GRB 211227A: Swift detection of a burst
- Swift GRB211227.98: Global MASTER-Net observations report
- IceCube-20211216B: observations of SN2021gpw in the errorbox of the neutrino trigger
- GRB 211226A: Swift/BAT-GUANO detection outside the coded FOV
- GRB 211225B: Swift-BAT refined analysis
- Fermi trigger No 662216114: Global MASTER-Net observations report
- GRB 211225A: MITSuME Akeno optical upper limits
- GRB 211226A: AGILE/MCAL detection of a burst
- Swift GRB 211225B: Global MASTER-Net observations report
- Fermi GRB 211225C: Global MASTER-Net observations report
- GRB 211225C: Fermi GBM Final Real-time Localization
- GRB 211225B: Swift detection of a burst
- MAXI GRB211225.14: Global MASTER-Net observations report
- GRB 211225A/MAXI J0827-071: MAXI/GSC detection
- Fermi trigger No 662084433: Global MASTER-Net observations report
- GRB 211224A: Fermi GBM Final Real-time Localization
- GRB 211106A: Third HST Observation
- GRB 211211A: observations with the 3.6m Devasthal Optical Telescope
- Fermi trigger No 662010159: Global MASTER-Net observations report
- GRB 211223C: Swift-BAT refined analysis
- AGILE observations of a bright burst from SGR 1935+2154
- GRB 211223C: BOOTES-4/MET optical upper limit
- Swift GRB 211223C: Global MASTER-Net observations report
- GRB 211223A: Insight-HXMT/HE detection
- Fermi GRB 211223B: Global MASTER-Net observations report
- Fermi GBM Sub-Threshold Detection of GRB 211221A
- Fermi GBM Sub-Threshold Detection of GRB 211207A
- GRB 211221A: Swift-BAT refined analysis
- GRB 211223C: Swift detection of a burst
- GRB 211223B: Fermi GBM Final Real-time Localization
- GRB 211223A: GECAM detection
- GRB 211221A: NUTTelA-TAO / BSTI Early Optical Limits (Preliminary)
- GRB 211219B: AstroSat CZTI detection
- GRB 211219A: AstroSat CZTI detection
- Fermi GRB 211222A: Global MASTER-Net observations report
- GRB 211221A: Swift-XRT refined Analysis
- GRB 211222A: Fermi GBM Final Real-time Localization
- GRB 211221A: BOOTES-4/MET optical upper limit
- GRB 211218A: MITSuME Akeno optical upper limits
- GRB 211221A: MeerLICHT optical limits
- GRB 211221A: NOT optical limits
- GRB 211221A: Enhanced Swift-XRT position
- Swift GRB 211221A: Global MASTER-Net observations report
- GRB 211221A: Swift detection of a burst
- IceCube-211216B: No significant detection in HAWC
- IceCube-211216A: No significant detection in HAWC
- GRB 211219A: AGILE detection
- GRB 211219A: Swift/BAT-GUANO detection outside the coded FOV
- Fermi GRB 211219B: Global MASTER-Net observations report
- GRB 211219B: Fermi GBM Final Real-time Localization