GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"- 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
- Fermi GRB 211219A: Global MASTER-Net observations report
- GRB 211219A: Fermi GBM Final Real-time Localization
- GRB 211211A: MMT/MMIRS Observations Indicate Fading of K-band Source
- GRB 211216A: Fermi GBM observation
- IceCube-211216B: No neutrino counterpart candidates in ANTARES search
- GRB 211218A, MAXI J0909-041: MAXI/GSC detection
- MAXI GRB211218.04: Global MASTER-Net observations report
- GRB 211106A: XMM-Newton monitoring campaign detections
- Fermi-LAT Gamma-ray Observations of IceCube-211216B
- Fermi-LAT Gamma-ray Observations of IceCube-211216A
- IceCube-211216B: Upper limits from Fermi-GBM Observations
- IceCube-211216A: Upper limits from Fermi-GBM Observations
- IceCube-211216A: Upper limits from a search for additional neutrino events in IceCube
- Fermi trigger No 661417475: Global MASTER-Net observations report
- IceCube-211216A: No neutrino counterpart candidates in ANTARES search
- GRB 211217A: GECAM detection
- GRB 211216A: Swift/BAT-GUANO detection outside the coded FOV
- IceCube-211216B - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 211216.99: Global MASTER-Net observations report
- Fermi GRB 211216B: Global MASTER-Net observations report
- GRB 211216B: GECAM detection
- IceCube Alert 211216.30: Global MASTER-Net observations report
- GRB 211216B: Fermi GBM Final Real-time Localization
- IceCube-211216A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
- GRB 211211A: TNG NIR observations
- IceCube-211216A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 211216A: GECAM detection
- GRB 211216A: BALROG localization (Fermi Trigger 661329957 / GRB 211216282)
- Fermi GRB 211216A: Global MASTER-Net observations report
- GRB 211216A: Fermi GBM Final Real-time Localization
- GRB 211211A: Insight-HXMT/HE detection
- GRB 211211A - Gemini K-band detection
- GRB 211211A: SAO RAS optical observations
- GRB 211211A: AbAO optical observations
- GRB 211211A: GMG upper limit
- Chandra observation of GW170817 at ~1575 days since merger (all epochs)
- GRB 211211A: redshift estimation and SPI-ACS/INTEGRAL detection
- GRB 211211A: Very fast decay observed from CAFOS/2.2mCAHA
- GRB 211211A: Further observations from CAFOS/2.2m CAHA
- GRB 211211A: HCT and GIT optical follow up observations
- GRB 211211A: CALET Gamma-Ray Burst Monitor detection
- IceCube-211208A: No neutrino counterpart detected with ANTARES
- Fermi GRB 211212A: Global MASTER-Net observations report
- GRB 211211A: incorrect E_iso value in GCN 31221
- GRB 211211A: Swift/UVOT detection
- GRB 211211A: NOT optical spectroscopy
- GRB 211211B: GECAM detection
- Fermi GRB 211212B: Global MASTER-Net observations report
- GRB 211211A: Afterglow detection from CAFOS/2.2m CAHA
- GRB 211211A: MITSuME Akeno optical observation
- Swift GRB 211211A: Global MASTER-Net observations report
- GRB 211212B: Fermi GBM Final Real-time Localization
- GRB 211211A: LCO Optical Observations
- GRB 211211A: Nanshan/NEXT optical observations
- GRB 211211A: Swift-XRT refined Analysis