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 210622A: Swift/BAT-GUANO detection and arcminute localization of a long burst
- GRB 210619B: possibility of lensed visible afterglow?
- GECAM detection of GRB 210622B
- GRB 210619B: AbAO optical observations
- GRB 210622B: Fermi GBM Final Real-time Localization
- GRB 210622A: Fermi GBM Final Real-time Localization
- Swift Trigger 1057131: detection of a burst from SGR Swift J1555.2-5402
- Swift GRB210621.71: Global MASTER-Net observations report
- GRB 210619B: NOT optical observations
- GRB 210619B: 1.5m OSN optical observation
- GRB 210619B: iTelescope optical afterglow observation
- GRB 210619B: SAO RAS optical observations
- GRB 210619B: SEDM Optical Observations
- GRB 210619B: TNG NIR observations of the afterglow
- GRB 210619B: REM optical/NIR afterglow detection
- Fermi GRB 210621A: Global MASTER-Net observations report
- GRB 210619B: GIT optical follow-up and confirmation of jet-break
- GRB 210621A: Fermi GBM Final Real-time Localization
- GRB 210619B: CALET Gamma-Ray Burst Monitor detection
- GRB 210619B: SRG/ART-XC detection
- GRB 210619B: Swift-BAT refined analysis
- GRB 210619B: steepening of the decay observed at the D50
- GRB 210619B: Liverpool Telescope First Hour Observations
- GRB 210619B: Fermi GBM detection
- GRB 210619B: Swift/UVOT Detection
- GRB 210619B: Xinglong TNT optical observations
- Konus-Wind detection of GRB 210619B
- GRB 210619B: CAHA 2.2m photometric monitoring
- GRB 210619B: Liverpool Telescope r'-band observations
- GRB 210619B: KAIT Optical Detection
- GRB 210619B: Redshift from OSIRIS/GTC
- GRB 210619B: Liverpool telescope imaging of a red afterglow
- GRB 210619B: Fermi-LAT detection
- GRB 210619B: Swift-XRT refined Analysis
- GRB 210619B: SARA-KP 0.9m Optical Afterglow Detection
- GRB 210619B: Enhanced Swift-XRT position
- Fermi trigger No 645857659: Global MASTER-Net observations report
- GRB 210619B: iTelescope T18 detection
- GECAM detection of GRB 210619B
- GRB 210619B: Ondrejov D50 detection
- Swift GRB210619.99: Global MASTER-Net OT detection
- GRB 210619B: Swift detection of a bright burst and optical counterpart
- Swift GRB210619.99: Global MASTER-Net observations report
- Swift GRB210619.99: Global MASTER-Net OT detection
- GRB 210619A: BALROG localization (Fermi Trigger 645799548 / GRB 210619532)
- GRB 210619A: Fermi GBM Final Real-time Localization
- GRB 210618A: Swift/UVOT Upper Limits
- GRB 210618A: BOOTES-2/TELMA optical upper limit
- GRB 210618A: Swift-BAT refined analysis
- GRB 210618A: Fermi GBM observation
- GRB 210618A: Swift-XRT observations
- GRB 210618A: DDOTI upper limit for the optical afterglow
- GRB 210618A: Swift detection of a burst
- Swift GRB210618.07: Global MASTER-Net observations report
- GRB 210618A: Fermi GBM Final Real-time Localization
- GRB 210610B: Swift/UVOT Detection
- GRB 210610A: Swift/UVOT Detection
- GRB 210610B: CrAO/ZTSH continued optical observations and light curve
- Fermi trigger No 645485036: Global MASTER-Net observations report
- GRB 210610B: AbAO optical observations
- GRB 201008A: Fermi GBM observation
- GRB 210323B: Fermi GBM observation
- Fermi GRB 210615A: Global MASTER-Net observations report
- GRB 210615A: Fermi GBM Final Real-time Localization
- GRB 210610B: REM optical/NIR observations of the afterglow
- Swift-BAT Trigger 1055000/GRB210612.54: MASTER optical source observation
- Follow-up on HAWC Transient Monitoring Alert J0020+3108
- Swift ToO Observations of HAWC transient J0020+3108
- GRB 210605B: Swift-XRT afterglow detection
- GRB 210610A: Fermi GBM observations
- GRB 210610A: CAHA 2.2m Second Epoch
- GRB 210610B: iTelescope optical afterglow observations
- GRB 210610B: Further SAO RAS optical observations
- GRB 210610A: SAO RAS optical observations
- GRB 210610B: optical observations from Burke-Gaffney Observatory and Abbey Ridge Observatory
- GRB 210610B: Continued KAIT Optical Detection
- GRB 210610B: optical photometry of afterglow at INASAN/Simeiz
- GRB 210421B: Fermi GBM detection
- Swift GRB210612.54: Global MASTER-Net observations report
- GRB 210607C: AstroSat CZTI detection
- Swift-BAT Trigger 1055000: Swift detection of an outburst from 4U 1543-47
- GRB210610B: SARA-KP 0.9m Optical Afterglow Detection
- GRB 210610B: MITSuME Akeno optical observation
- GRB 201228B: Fermi GBM observation
- GRB 210610B: VLA detection
- GRB 210610B: ALMA detection
- GRB 210610B: Liverpool Telescope optical photometry
- GRB 210610B: CrAO/ZTSH optical observations and light curve
- GRB 210610A: CrAO/ZTSH optical observations
- GRB 210610B: CrAO/ZTSH optical observations (correction to the GCN circ. 30212)
- GRB 210610A: CrAO/ZTSH optical observations
- GRB 210610A: CAHA 2.2m observations and light-curve behavior
- GRB 210606A: Fermi GBM detection
- GRB 210605B: Fermi GBM detection
- GRB 210610B: Swift-XRT refined Analysis
- GRB 210610B: Swift-BAT refined analysis
- GRB 210610B: Zwicky Transient Facility afterglow detection
- GRB 210610B: optical afterglow observations
- GRB 210610B: KAIT Optical Detection
- GRB 210610A: KAIT Optical Detection