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"21393 results found.
- GRB 260114A: GMG Optical Observation
- GRB 260114A: Swift detection of a short burst
- Swift GRB260113.43: Global MASTER-Net observations report
- 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: Fermi GBM Observation
- Swift Trigger 1434591 is not a GRB
- GRB 260111A: Swift ToO observations
- GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
- Swift trigger 1436759 is not an astrophysical event
- GRB 260109C: LCO optical upper limits
- GRB 260109C: Kilonova-Catcher optical upper limit
- Swift Trigger 1434591: possible GRB 260109C
- GRB 260102A: Swift-XRT afterglow detection
- GRB 260104A: Swift-BAT refined analysis
- GRB 260101A: Swift-BAT refined analysis
- Swift GRB 251230A: Global MASTER-Net OT detection
- GRB 260104A: COLIBRÍ optical upper limits
- Swift GRB 260104A: Global MASTER-Net observations report
- GRB 260104A: Swift-XRT refined Analysis
- GRB 260104A: Enhanced Swift-XRT position
- GRB 260101A: Swift/UVOT Detection
- GRB 260104A: Swift detection of a burst
- GRB 260102A: LCO optical upper limits
- GRB 260102A: Swift-XRT observations
- 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
- GRB 260101A: GECAM-B detection
- GRB 260101A: NOT spectroscopic observations
- GRB 260101A: SVOM/GRM observation
- GRB 260101A: Swift-XRT refined Analysis
- Swift GRB 260101A: Global MASTER-Net observations report
- GRB 260101A: Enhanced Swift-XRT position
- GRB 260101A: LCO detection of the optical counterpart
- GRB 260101A: Swift detection of a burst with an optical counterpart
- GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
- GRB 251230A: GRANDMA/TAROT Early Detection
- GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
- GRB 251230A/EP251230a: Optical upper limit with Kinder observations
- GRB 251230A: 1.3m DFOT optical upper limit
- GRB 251230A: Swift-XRT refined Analysis
- EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
- GRB 251230A: Swift/UVOT detection
- GRB251230A: 7DT optical upper limits
- GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
- GRB 251230A: GOTO optical upper limit
- GRB 251230A / EP251230a: SVOM/VT optical observation
- GRB 251230A: Enhanced Swift-XRT position
- GRB 251230A: Early optical counterpart detection by LCO.
- EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
- GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
- Swift GRB 251230A: Global MASTER-Net observations report
- GRB 251230A: Swift detection of a burst with a bright optical counterpart
- GRB 251222A/EP251222b: Optical detection with Kinder observations
- GRB 251221A: Swift-BAT refined analysis
- GRB 251205A: Kilonova-Catcher optical afterglow detection
- GRB 251129A / EP251129a: VLA detection of a radio counterpart
- GRB 251222A: Fermi GBM Observation
- GRB 251222A: Swift-XRT afterglow detection
- GRB 251222A / EP251222b: LCO detection of the optical counterpart
- GRB251221A: 7DT optical upper limits
- IPN triangulation of GRB 251220B (short)
- GRB 251222A: Swift ToO observations
- GRB 251221A: PRIME near-infrared observation
- GRB 251221A: UAFO and Mondy optical upper limit
- GRB 251221A: Swift-XRT refined Analysis
- GRB 251221A: Swift/UVOT Upper Limits
- GRB 251221A: Enhanced Swift-XRT position
- GRB 251221A: Fermi GBM Observation
- GRB 251221A: COLIBRÍ detection of the optical counterpart
- GRB 251221A: Swift detection of a burst
- Swift GRB251221A: Global MASTER-Net observations report
- GRB 251215A: Swift-XRT afterglow detection
- GRB 251214B: VIRT Optical Upper Limit
- GRB 251215A: Swift/UVOT Upper LImits
- GRB 251215A: Fermi GBM Observation
- GRB 251214B: Mondy optical upper limit
- GRB 251215A: COLIBRÍ optical upper limit
- GRB 251215A: Swift-XRT observations
- GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
- GRB 251215A: Glowbug gamma-ray detection
- GRB 251214B: UAFO optical upper limit
- GRB 251214B: VLT/X-shooter observations
- GRB 251214B: Swift-BAT refined analysis
- GRB 251202A: radio detection with the VLA
- GRB 251214B: AbAO optical observations
- GRB 251214B: LCO detection of the optical counterpart
- GRB 251214B: Fermi GBM Observation
- GRB 251215A: Swift ToO observations
- EP251214b (EP trigger 01709250023): LCO optical limits
- GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251214B: Swift-XRT refined Analysis
- GRB 251214B: Swift/UVOT Detection
- GRB 251214B: COLIBRÍ observations of the afterglow
- GRB 251214B: 1.3m DFOT optical detection