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').
- MAXI GRB210521.54: Global MASTER-Net observations report
- GRB 210521A: MAXI/GSC detection
- GRB210413B: further Swift-XRT observations
- GRB 210520A: Fermi GBM detection
- ZTF21aayokph (AT2021lfa): continued Assy optical observations
- GRB 210520A: Tiled Swift observations
- GRB 210520A: Fermi-LAT detection
- GRB 210520A: GECAM detection
- Fermi GRB 210520A: Global MASTER-Net observations report
- GRB 210520A: Fermi GBM Final Real-time Localization
- Fermi GBM observation of a bright burst from magneta
- GRB 210517A: KCT optical upper limit
- IceCube GCN alert 135302_36915486.amon retraction
- Fermi GRB 210519A: Global MASTER-Net observations report
- IceCube Alert 210519.86: Global MASTER-Net observations report
- IPN triangulation of GRB 210518A
- Fermi trigger No 643065622: Global MASTER-Net observations report
- GRB 210518.889: DDOTI Upper Limits on the Afterglow
- GRB 210519A: Fermi GBM Final Localization
- Fermi GRB 210518A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 210514A
- Fermi trigger No 642991619: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-210516A
- GRB 210518A: Fermi GBM Final Real-time Localization
- IceCube Alert 210515.01: Global MASTER-Net observations report
- GRB 210517A: Swift-BAT refined analysis
- GRB 210517A: Swift-XRT refined Analysis
- IceCube-210516A: No significant detection in HAWC
- GRB 210517A: Swift/UVOT Upper Limits
- GRB 210515C: Swift/UVOT Upper Limits
- IceCube-210516A: Upper limits from a search for additional neutrino events in IceCube
- GRB 210517A: VLT/X-shooter optical afterglow and redshift
- GRB 210517A: AGILE detection
- GRB 210514A: CALET Gamma-Ray Burst Monitor detection
- GRB 210517A: Enhanced Swift-XRT position
- Swift GRB 210517A: Global MASTER-Net observations report
- GRB 210517A: Swift detection of a burst
- Fermi GRB 210516A: Global MASTER-Net observations report
- GRB 210516A: Fermi GBM Final Real-time Localization
- IceCube Alert 210516.61: Global MASTER-Net observations report
- GRB 210515C: LCO Optical Upper Limit
- GRB 210504A: LCO Optical Afterglow Detection
- IceCube-210516A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 210514A: Swift/UVOT Upper Limits
- AMON IC_HAWC NuEm-210515A / NuEm-210515B : No neutrino counterpart detected with ANTARES
- GRB 210515C: Swift-XRT refined Analysis
- Swift GRB210515.83: Global MASTER-Net observations report
- GRB 210515C: Swift-BAT refined analysis
- GRB 210515C: Swift detection of a burst
- Fermi GRB 210515B: Global MASTER-Net observations report
- GRB 210514A: Swift-BAT refined analysis
- Fermi GRB 210515A: Global MASTER-Net observations report
- GRB 210515B: Fermi GBM Final Real-time Localization
- GRB 210515A: Fermi GBM Final Real-time Localization
- Swift GRB210514.71: Global MASTER-Net observations report
- GRB 210514A: Swift XRT light curve is fading
- GRB 210514A: Swift-XRT refined Analysis
- GRB 210514A: Enhanced Swift-XRT position
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEM-210515A and 210515B
- GRB 210514A: update on the BAT trigger time and burst duration
- GRB 210514A: Swift detection of a burst
- Konus-Wind detection of GRB 210511B
- GRB 210512.786: DDOTI Upper Limits on the Afterglow
- GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
- Fermi trigger No 642538568: Global MASTER-Net observations report
- IceCube-210510A: Upper limits from a search for additional neutrino events in IceCube
- IPN triangulation of GRB 210511B
- IceCube-210510A: not observable by Fermi-GBM
- Short GRB 210323A: likely host galaxy detection
- IceCube-210510A: No candidate counterparts from the Zwicky Transient Facility
- GRB 210511B: DDOTI Upper Limits on the Afterglow
- IPN triangulation of GRB 210427A
- GRB 210511B: Fermi GBM observation
- Fermi-LAT Gamma-ray Observations of IceCube-210510A
- Fermi GRB 210511A: Global MASTER-Net observations report
- Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
- Fermi GRB 210511B: Global MASTER-Net observations report
- GRB 210511B: AGILE detection
- GRB 210511B: GECAM detection
- GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
- GRB 210511B: Fermi GBM Final Real-time Localization
- GRB 210511A: Fermi GBM Final Real-time Localization
- Fermi GRB 210510A: Global MASTER-Net observations report
- GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
- GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
- Swift trigger 1047857 is 4U 1700-377
- IceCube Alert 210510.20: Global MASTER-Net observations report
- GRB 210510A: Fermi GBM Final Real-time Localization
- IceCube-210510A: DDOTI Upper Limits
- GRB 210509A: RATIR Optical and NIR Upper Limits
- GRB 210509A: Swift/UVOT Upper Limits
- GRB 210509A: Swift-XRT refined Analysis
- IceCube-210510A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 210509A: Swift-BAT refined analysis
- Swift GRB 210509A: Global MASTER-Net observations report
- GRB 210509A: Enhanced Swift-XRT position
- GRB 210509A: BOOTES-4/MET optical upper limit
- GRB 210509A: Swift-XRT observations
- GRB 210509A: Swift detection of a burst
- GRB 210506A: Swift/BAT-GUANO position retraction