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"- EP260110a: NOT and GTC Optical and Near-Infrared Observations
- EP260110a: TRT optical upper limits
- Konus-Wind detection of GRB 260101A
- GRB 260111A: Swift-XRT observations
- Swift Trigger 1439093: is probably not GRB 260113A
- GRB 260111A: COLIBRÍ optical afterglow candidate
- GRB 260111A: GECAM-B observation of a burst
- GRB 260111A: Fermi GBM Observation
- The EP-WXT trigger 01709251266 is likely a flaring star
- Swift Trigger 1434591 is not a GRB
- GRB 260111A: GOTO optical upper limits
- GRB 260112B: Fermi GBM Final Real-time Localization
- GRB 260111A: Swift ToO observations
- GRB 251230A: Mondy Optical Observations
- GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 260112A: Fermi GBM Final Real-time Localization
- EP260110a: SVOM/VT optical upper limits
- IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 260111A: Global MASTER-Net observations report
- EP260110a: Global MASTER-Net observations report
- Fermi GRB 260111A: Global MASTER-Net observations report
- GRB 260111A: Fermi GBM Final Real-time Localization
- Swift trigger 1436759 is not an astrophysical event
- EP260110a: KAIT optical upper limit
- EP260110a: refined analysis of the EP-WXT and EP-FXT observations
- EP 260110a: COLIBRÍ optical observations
- EP260110a: SVOM/C-GFT upper limit
- EP260110a: BOOTES-5/JGU optical upper limit
- EP260110a: Einstein Probe detection of an X-ray transient
- GRB 260109C: LCO optical upper limits
- GRB 260109C: Kilonova-Catcher optical upper limit
- EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
- Swift Trigger 1434591: possible GRB 260109C
- GRB 260109B: Fermi GBM Final Real-time Localization
- GRB 260102A: Swift-XRT afterglow detection
- GRB 260109A: Fermi GBM Final Real-time Localization
- GRB 260104A: Swift-BAT refined analysis
- GRB 260101A: Swift-BAT refined analysis
- Swift GRB 251230A: Global MASTER-Net OT detection
- Fermi GRB 260107A: Global MASTER-Net observations report
- GRB 260102A: AbAO optical observations
- GRB 260107A: Fermi GBM Final Real-time Localization
- EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
- The EP-WXT trigger 01709251112 is likely a flaring star
- Fermi GRB 260105A: Global MASTER-Net observations report
- GRB 260105B: Fermi GBM Detection
- EP260105a: FTW optical observations
- EP260104a: FTW optical observations
- GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
- GRB 260105A: SVOM/GRM observation
- GRB 260105B: SVOM/GRM observation
- The EP-WXT trigger 01709251028 is likely a flaring star
- FRB 20251229A: COLIBRÍ optical upper limits
- Fermi GRB 260105B: Global MASTER-Net observations report
- EP260105a: SVOM/VT optical upperlimit
- GRB 260105B: Fermi GBM Final Real-time Localization
- GRB 260105A: Fermi GBM Final Real-time Localization
- FRB 20251229A: A potentially hyperactive repeating fast radio burst source
- EP260105a: refined analysis of the EP-WXT and EP-FXT observations
- EP260105a: LCO Optical Upper limit
- EP260104a: Global MASTER-Net observations report
- EP260104a: Einstein Probe detection of a fast X-ray transient
- GRB 260101A: COLIBRÍ optical upper limits
- EP260105a: Global MASTER-Net observations report
- EP260105a: Einstein Probe detection of an X-ray transient
- GRB 260103A: Insight-HXMT/HE detection
- GRB 260104A: COLIBRÍ optical upper limits
- GRB 260104C: Fermi GBM Final Real-time Localization
- Fermi GRB 260104B: Global MASTER-Net observations report
- Swift GRB 260104A: Global MASTER-Net observations report
- GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
- GRB 260104A: Swift-XRT refined Analysis
- GRB 260104A: Enhanced Swift-XRT position
- GRB 260101A: Swift/UVOT Detection
- GRB 260103A: GECAM-B observation of a burst
- GRB 260104B: Fermi GBM Final Localization
- GRB 260104A: Swift detection of a burst
- GRB 260103A: SVOM/GRM observation of a possible GRB
- Fermi-LAT Gamma-ray Observations of IceCube-251225A
- GRB 260101A: COLIBRÍ optical observations
- SVOM GRB260103.08: Global MASTER-Net observations report
- GRB 260102B: Fermi GBM Final Real-time Localization
- SVOM GRB260102A: Global MASTER-Net observations report
- Fermi GBM Sub-Threshold Detection of GRB 260102A
- GRB 260102A: EP-FXT follow-up observation
- EP260101a: Global MASTER-Net observations report
- GRB 260102A: LCO optical upper limits
- GRB 260102A: Swift-XRT observations
- GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
- Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
- GRB 251230A / EP251230a: GECAM-B detection
- GRB 260102A: SVOM/VT optical counterpart
- GRB 251230A / EP251230a: Insight-HXMT/HE detection
- GRB 260102A: Swift ToO observations
- GRB 260101A: Fermi GBM Observation
- EP260101a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260102A: SVOM detection of a burst
- GRB 260101A: GECAM-B detection
- GRB 260101A: NOT spectroscopic observations
- GRB 260101A: SVOM/GRM observation