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').
- Trigger 1160641: Swift detection of 4U 1630-472 (a.k.a. SWIFT J1633.8-4724A)
- Fermi trigger No 700976129: Global MASTER-Net observations report
- GRB 230307A: Continued Gemini-South observations confirm rapid optical fading
- IPN triangulation of GRB 230309A
- Fermi GRB 230316A: Global MASTER-Net observations report
- GRB 230304D: AstroSat CZTI detection
- GRB 230316A: Fermi GBM Final Real-time Localization
- IPN triangulation of GRB 230304B
- GRB 230313A: AstroSat CZTI detection
- GRB 230307A: Far off-axis NuSTAR detection of the GRB
- IPN triangulation of GRB 230308A (short/bright)
- Fermi GRB 230314A: Global MASTER-Net observations report
- GRB 230307A: ATCA radio detection
- GRB 230314A: Fermi GBM Final Real-time Localization
- VZLUSAT-2 detection of SGR 1806-20
- GRB 230307A: INTEGRAL upper limit on Hard X-ray afterglow
- GRB 230307A: Swift/UVOT detection
- AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230313A
- GRB 230313A: BALROG localization (Fermi Trigger 700400328 / GRB 230313485)
- Fermi GRB 230313A: Global MASTER-Net observations report
- GRB 230313A: Fermi GBM Final Real-time Localization
- GRB 230307A: soft X-ray detection with LEIA
- GRB 230307A: Swift-XRT afterglow detection
- GRB 230309A: AstroSat CZTI detection of a bright long GRB
- Swift GRB230311.85: Global MASTER-Net observations report
- Swift GRB230311.83: Global MASTER-Net observations report
- Further improved IPN localization for GRB 230307A
- Swift GRB230311.81: Global MASTER-Net observations report
- GRB 230307A: SOAR/Goodman detection of the possible host galaxy
- Swift GRB230311.84: Global MASTER-Net observations report
- Swift Trigger 1159438 is also due to the Star Tracker loss of lock.
- Swift GRB230311.82: Global MASTER-Net observations report
- Triggers 1159434, 1159435 and 1159437: Swift detection of Sco X-1 due to Star Tracker loss of lock
- Alert from the HAWC Burst Monitor HAWC-230311A
- TESS Detection of the Optical Afterglow of GRB230307A
- GRB 230308A: CALET Gamma-Ray Burst Monitor detection
- Trigger 1159327: Swift detection of SGR1806-20
- GRB 230310A: AstroSat CZTI detection
- GRB 230307A: GECKO optical observations and detections of the afterglow
- GRB 230307A: MAXI/GSC upper limit
- GRB 230307A: Gemini-South Confirmation of the Optical Afterglow
- Fermi GRB 230310A: Global MASTER-Net observations report
- GRB 230310A: Fermi GBM Final Real-time Localization
- GRB 230307A: AGILE/MCAL analysis
- GRB 230307A: ATLAS information on the ULTRACAM optical afterglow candidate
- GRB 230307A: Erratum of the GCN 33441
- GRB 230204B: MASTER detection of an object near NTT Optical Afterglow Candidate
- GRB 230308A: Fermi GBM detection
- GRB 230307A: Possible optical afterglow
- GRB 230307A: ASO-S/HXI detection
- GRB 230307A: AstroSat LAXPC detection
- GRB 230228A: NUTTelA-TAO / BSTI Optical Limits
- GRB 230308A: AGILE/MCAL detection
- GRB 230307A: optical upper limit
- GRB 230217A: ATCA rapid-response radio detection
- Swift Trigger 1159108 is not a GRB
- GRB 230307A: Swift/BAT upper limits on the early afterglow
- GRB 230307A: Upper limits from a neutrino search with IceCube
- GRB 230307A: Swift-XRT observations
- Fermi GRB 230307A: Global MASTER-Net observations report
- Konus-Wind detection of GRB 230307A
- GRB 230228A: VIRT Optical Upper Limit
- Improved IPN localization for GRB 230307A
- GRB 230307A: VZLUSAT-2 detection
- GRB 230304B: CALET Gamma-Ray Burst Monitor detection
- Fermi GRB 230308A: Global MASTER-Net observations report
- GRB 230308A: BALROG localization (Fermi Trigger 699975152 / GRB 230308564)
- GRB 230308A: Fermi GBM Final Real-time Localization
- GRB 230307A: Tiled Swift observations
- GRB 230307A: Detection by GRBAlpha
- GRB 230305A: Detection by GRBAlpha
- GRB 230307A: BALROG localization (Fermi Trigger 699896651/ GRB 230307656)
- GRB 230307A: AstroSat CZTI detection
- GRB 230307A: possibly the second highest GRB energy fluence ever identified
- IPN triangulation of GRB 230307A (long/very bright)
- GRB 230307A: AGILE/MCAL detection
- GRB 230307A: Fermi GBM Observation of a very bright burst
- Solar Orbiter STIX observation of GRB 230307A
- IceCube-230306A: Upper limits from a search for additional neutrino events in IceCube
- Fermi-LAT gamma-ray observations of IceCube-230306A
- GRB 230307A: Fermi GBM detection of a very bright GRB
- GRB 230307A: GECAM detection of an extremely bright burst
- GRB 230307A: Fermi GBM Final Real-time Localization
- Fermi trigger No 699811746: Global MASTER-Net observations report
- IceCube-230306A - IceCube observation of a high-energy neutrino candidate
- IceCube Alert 230306.46: Global MASTER-Net observations report
- GRB 230304C: AstroSat CZTI detection
- GRB 230304B: AstroSat CZTI detection
- GRB 230304A: AstroSat CZTI detection
- GRB 230304B: Detection by GRBAlpha
- GRB 230304C: Fermi GBM Final Real-time Localization
- GRB 230304B: Fermi GBM Final Real-time Localization
- GRB 230304A: Fermi GBM Final Real-time Localization
- GRB 230228A: 6 GHz VLA radio upper limit
- GRB 230228A: Swift-BAT refined analysis
- GRB 230228A: Swift/UVOT Upper Limits
- Fermi GRB 230301B: Global MASTER-Net observations report
- GRB 230301B: Fermi GBM Final Real-time Localization
- GRB 230228A: Fermi GBM Observation
- Fermi trigger No 699294715: Global MASTER-Net observations report