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').
- 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