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"- Fermi GRB 210317A: Global MASTER-Net observations report
- GRB 210317A: GECAM detection
- GRB 210317A: Fermi GBM Final Real-time Localization
- Fermi trigger No 637521056: Global MASTER-Net observations report
- GRB 210306A: GIT optical follow-up
- GRB 210226A: GIT optical upper limit
- GRB 210312B: Redshift from OSIRIS/GTC
- GRB 210306A: HCT optical upper limit
- GRB 210312B: GTC photometry
- GRB 210312B: MASTER OT confirmation
- GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
- GRB 210312B: A long GRB detected by INTEGRAL
- Integral GRB210312.87: Global MASTER-Net observations report
- Fermi GRB 210312A: Global MASTER-Net observations report
- INTEGRAL SPI-ACS on 2021-03-12 (04)11-08:15) are due to calibration activity
- GRB 210312A: Fermi GBM Final Real-time Localization
- GRB 210306A: LBT observations
- GRB 210306A: Tautenburg observations
- Konus-Wind detection of GRB 210308A
- Konus-Wind detection of GRB 210306A
- Konus-Wind detection of GRB 210305A
- GRB 171205A: Continued ATCA observations
- Fermi trigger No 637027080: Global MASTER-Net observations report
- GRB 210306A: Early Spectroscopy of the Optical Afterglow
- GRB 210306B: Fermi GBM detection
- GRB 210306A: Swift/UVOT Detection
- GRB 210306A: continued Mondy optical observations
- GRB 210308A: Mondy and AbAO optical observations
- GRB 210308A: Swift-BAT refined analysis
- GRB 210307A: Swift-BAT refined analysis
- Fermi trigger No 636926765: Global MASTER-Net observations report
- GRB 210308A: Swift/UVOT Detection
- GRB 210307A: Swift/UVOT Upper Limits
- GRB 210305A: Fermi GBM observation
- Swift GRB 210308A: Global MASTER-Net observations report
- GRB 210308A: Fermi GBM detection
- GRB 210305A: Swift-XRT refined Analysis
- GRB 210307A: Swift-XRT refined Analysis
- GRB 210308A: Nanshan/NEXT optical upper limits
- GRB 210306A: Swift-XRT refined Analysis
- GRB 210308A: MITSuME Okayama optical upper limits
- GRB 210306A: continued Mondy optical observations
- GRB 210308A: Swift detection of a burst with an optical counterpart
- GRB 210306A: 1.3m DFOT observations
- GRB 210306A: Swift-BAT refined analysis
- GRB 210306A: Mondy optical observations
- GRB 210305A: Swift/UVOT Upper Limits
- GRB 210307B: GECAM detection
- GRB 210307A: LCO Optical Upper Limits
- GRB 210306B: Swift-BAT refined analysis
- GRB 210305A: Swift-BAT refined analysis
- GRB 210307A: Swift detection of a burst
- Swift GRB210307.36: Global MASTER-Net observations report
- GRB 210306A: MITSuME Akeno optical observation
- GRB 210306A: NEXT optical observations
- Swift GRB 210306A: Global MASTER-Net observations report
- GRB 210306A: Fermi GBM observation
- GRB 210306A: Tautenburg observations
- GRB 210306A: iTelescope T24 optical observations
- GRB 210306A: Fermi-LAT detection
- GRB 210306B: Swift detection of a burst
- GRB 210306A: LCO Optical Afterglow Detection
- GRB 210306A: iTelescope optical afterglow observations
- GRB 210306A: DDOTI Afterglow Confirmation
- GRB 210306A: Swift detection of a burst with a bright optical counterpart
- Swift GRB 210305A: Global MASTER-Net observations report
- GRB 210305A: Swift detection of a burst
- GRB 210228B: Insight-HXMT/HE detection
- Trigger 1035744: Swift detection of Sco X-1 due to Star Tracker loss of lock
- Fermi trigger No 636459103: Global MASTER-Net observations report
- GRB 210217A: 3.6m DOT optical observations
- GRB 210226A: Swift/UVOT Upper Limits
- Fermi trigger No 636187116: Global MASTER-Net observations report
- GRB 210228A: GECAM detection
- Fermi trigger No 636168178: Global MASTER-Net observations report
- Integral GRB210227.20: Global MASTER-Net observations report
- Integral GRB210227.19: MASTER OT retraction
- GRB 210225A: Insight-HXMT/HE detection
- INTEGRAL IBAS Alert n.9020 not a GRB
- Integral GRB210227.20: Global MASTER-Net observations report
- Integral GRB210227.19: Global MASTER-Net observations report
- Integral GRB210227.19: Global MASTER-Net OT detection
- GRB 210226A: Swift-BAT refined analysis
- GRB 210226A: Fermi GBM detection
- GRB 210217A: Mondy optical observations
- GRB 210226A: KAIT Optical Upper Limit
- GRB 210226A: Swift-XRT refined Analysis
- Swift GRB 210226A: Global MASTER-Net observations report
- GRB 210218A: Swift-XRT confirmation of afterglow
- GRB 210226A: Burke-Gaffney Observatory optical upper limit
- GRB 210226A: Enhanced Swift-XRT position
- GRB 210226A: Ondrejov BART/SBT optical limit
- GRB 210222B: 1.3m DFOT Optical upper limit
- GRB 210226A: Swift detection of a burst
- GRB 210222B: REM observations of the optical/NIR afterglow
- Fermi trigger No 635922820: Global MASTER-Net observations report
- GRB 210222B: MITSuME Akeno optical upper limits
- Konus-Wind detection of GRB 210222A
- GRB 210222B: Zeiss-1000 of Koshka observatory, optical observations
- GRB 210222B: VIRT optical detection