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.
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
- Swift GRB 210610A: Global MASTER-Net observations report
- Swift GRB 210610A: MASTER optical counterpart observation
- GRB 210610A: Enhanced Swift-XRT position
- GRB 210610A: Xinglong-2.16m redshift
- GRB 210610A: GIT optical detection
- GRB 210610A: Xinglong-2.16m optical afterglow observations
- GRB 210610A: MITSuME Akeno optical observation
- GRB 210610A: Swift detection of a burst with an optical counterpart
- GRB 210607B: Insight-HXMT/HE detection
- GRB 210605A: CALET Gamma-Ray Burst Monitor detection
- Konus-Wind detection of GRB 210606B
- Fermi-LAT Gamma-ray Observations of IceCube-210608A
- IceCube-210608A: not observable by Fermi-GBM
- IPN triangulation of GRB 210606B
- IceCube-210608A: IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 210608.15: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 644793834 / 210607892 is not a GRB
- GRB 210607A/MAXI J1733-222: MAXI/GSC detection
- MAXI GRB210607.82: Global MASTER-Net observations report
- Fermi trigger No 644793834: Global MASTER-Net observations report
- GRB 210606B: Fermi GBM detection
- GRB 210605B: Swift-XRT observations
- Konus-Wind detection of GRB 210602A
- Konus-Wind detection of GRB 210605A (short/hard)
- IPN triangulation of GRB 210605A (short)
- GRB 210606B: AGILE detection
- GRB 210606A: 1.5m OSN optical upper limit
- GECAM Sub-Threshold Detection of new magnetar Swift SGR J1555.2-5402
- GRB 210606B: BALROG localization (Fermi Trigger 644712030 / GRB 210606945)
- GRB 210606B: GECAM detection
- Fermi trigger No 644712030: Global MASTER-Net observations report
- GRB 210606A: Swift ToO observations
- Fermi GRB 210606A: DDOTI Upper Limits on the Afterglow
- GRB 210606A: Swift/BAT-GUANO detection and arcminute localization
- GRB 210605B: Swift ToO observations
- Fermi GRB 210606A: Global MASTER-Net observations report
- GRB 210606A: Fermi GBM Final Real-time Localization
- GRB 210605B: Swift/BAT-GUANO detection and arcminute localization
- GRB 210605B: Fermi GBM Final Real-time Localization
- Fermi GRB 210605A: Global MASTER-Net observations report
- GRB 210605A: Fermi GBM Final Real-time Localization
- Initial results of a NICER X-ray monitoring of the magnetar, Swift J1555.2-5402
- Fermi GBM Sub-Threshold Detection of new Swift SGR J1555.2-5402
- SGR J1555.2-5402: Swift-BAT refined analysis
- Fermi trigger No 644449593: Global MASTER-Net observations report
- Swift J1555.2-5402: Swift XRT refined analysis of the new SGR
- NICER discovery of 3.86 s pulsations from a new magnetar: SGR J1555.2-5402
- Swift Detection of probable new Swift SGR J1555.2-5402
- MAXI GRB210602.50: Global MASTER-Net observations report
- Swift GRB210603.41: Global MASTER-Net observations report
- GRB 210602A: CALET Gamma-Ray Burst Monitor detection
- GRB 210602B: GECAM detection
- GRB 210529A: GECAM detection
- Fermi trigger No 644359567: Global MASTER-Net observations report
- GRB 210602A: MAXI/GSC detection
- Fermi GRB 210601A: Global MASTER-Net observations report
- GRB 210601A: Fermi GBM Final Real-time Localization
- IPN triangulation of GRB 210531A
- GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
- GRB 210531A: AstroSat CZTI detection
- Fermi trigger No 644155206: Global MASTER-Net observations report
- GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
- GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
- GRB 210529B: DDOTI Upper Limits on the Afterglow
- Fermi GRB 210529A: Global MASTER-Net observations report
- Fermi GRB 210529B: Global MASTER-Net observations report
- GRB 210529B: Fermi GBM Final Real-time Localization
- GRB 210529A: Fermi GBM Final Real-time Localization
- GRB 210528A: Fermi GBM detection
- GRB 210528A: AstroSat CZTI detection
- GRB 210528B: DDOTI Upper Limits on the Afterglow
- GRB 210528B: MITSuME Akeno optical upper limits
- MAXI GRB210528.95: Global MASTER-Net observations report
- GRB 210528B: MAXI/GSC detection
- Fermi GRB 210528A: Global MASTER-Net observations report
- GRB 210527A: Swift-BAT refined analysis
- GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
- GRB 210528A: Fermi GBM Final Real-time Localization
- GRB 210527A: Swift/UVOT Observations
- GRB 210527A: GIT optical upper limit
- GRB 210527A: MITSuME Akeno optical upper limits
- Swift GRB 210527A: Global MASTER-Net observations report
- GRB 210527A: Swift-XRT refined Analysis
- GRB 210527A: RATIR Optical and NIR Observations
- GRB 210527A: Enhanced Swift-XRT position
- GRB 210527A: Swift-XRT observations
- GRB 210527A: Swift detection of a burst
- GRB 210306A: LBT observations of the likely host galaxy
- ZTF21aayokph (AT2021lfa): LBT optical observations
- Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
- Konus-Wind detection of GRB 210524A
- IPN triangulation of GRB 210524A
- Fermi trigger No 643548039: Global MASTER-Net observations report
- GRB 210524B: Fermi GBM Final Real-time Localization
- GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
- Fermi GRB 210524A: Global MASTER-Net observations report
- GRB 210524A: Fermi GBM Final Real-time Localization
- GRB 210522A: GECAM detection
- GRB 210520A: Swift-XRT observations
- MAXI GRB210521.54: Global MASTER-Net observations report