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"36948 results found.
- GRB 250911A: Enhanced Swift-XRT position
- GRB 250911A: Swift-XRT observations
- GRB 250911A: COLIBRÍ optical counterpart candidate
- GRB 250911A: Swift detection of a burst
- GRB 250910B: BALROG localization (Fermi Trigger 779223130 / GRB 250910786)
- GRB 250910B: Fermi GBM Final Real-time Localization
- GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
- EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
- GRB 250909B: AstroSat CZTI detection of a long burst
- GRB 250910A: SVOM/VT optical upper limit
- GRB 250910A: LCO optical upper limit
- GRB 250909A: AstroSat CZTI detection
- GRB 250910A: SVOM/MXT possible afterglow detection
- GRB 250910A: SVOM detection of a faint burst
- GRB 250702B: Late time Chandra observations
- EP250908b/EP#01709240653: Swift/UVOT Detection
- EP#01709240653: Swift-XRT observations
- GRB 250907A: CALET Gamma-Ray Burst Monitor detection
- Fermi GRB 250909A: Global MASTER-Net observations report
- GRB 250909A: Fermi GBM Final Real-time Localization
- GRB 250907A: GECAM-B detection
- GRB 250905A: Swift-BAT refined analysis
- GRB 250903A: Swift-XRT afterglow detection
- GRB 250905A: Swift-XRT refined Analysis
- GRB 250904A: Swift-BAT refined analysis
- GRB 250905A: Swift/UVOT Upper Limits
- GRB 250901A - SVOM/ECLAIRs refined analysis
- GRB 250905B: Fermi GBM Final Localization
- GRB 250905A: Enhanced Swift-XRT position
- GRB 250904A: Swift/UVOT Detection
- GRB 250903A: Swift/UVOT detection
- GRB 250904A: Swift-XRT refined Analysis
- GRB 250905A: KAIT optical upper limit
- GRB 250905A: Swift detection of a burst
- Swift GRB250905.09: Global MASTER-Net observations report
- Swift GRB 250904A: Global MASTER-Net observations report
- GRB 250904A: Enhanced Swift-XRT position
- GRB 250904A: TRT optical counterpart detection
- EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
- GRB 250902B: CALET Gamma-Ray Burst Monitor detection
- GRB 250904A: Prompt enhanced Swift-XRT position
- GRB 250904A: Swift detection of a burst
- GRB 250902A: CALET Gamma-Ray Burst Monitor detection
- GRB 250902A: VZLUSAT-2 detection
- GRB 250903A: Swift-XRT observations
- EP250903a: Swift-XRT observations
- EP#01709201209: Swift-XRT observations
- EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
- GRB 250830C: VZLUSAT-2 detection
- GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
- GRB 250903A: EP-FXT counterpart detection
- GRB 250902A: GECAM-B detection
- GRB 250903A: LCO optical observation
- GRB 250903A: LCO optical afterglow detection
- GRB 250903A: SVOM/VT optical confirmation with VHF data
- EP250901a: Mondy, Assy and SAO RAS optical limits
- Subject GRB 250903A: SVOM/MXT afterglow detection
- GRB 250903A: TRT optical counterpart detection
- GRB 250902B: AstroSat CZTI detection
- GRB 250903A: SVOM detection of a burst
- EP 250827B: Detection of supernova counterpart by LCO.
- EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
- GRB 250902B: SVOM/GRM observation
- GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
- Fermi GRB 250902B: Global MASTER-Net observations report
- GRB 250902A: Fermi GBM Detection
- GRB 250901A: Swift/UVOT Upper Limit
- GRB 250902B: Fermi GBM Final Real-time Localization
- GRB 250830B: Swift-XRT afterglow detection
- GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
- GRB 250902A: SVOM/GRM observation
- GRB 250901A: EP-FXT follow-up observation
- GRB 250901A: NOT optical observations
- GRB 250902A: Fermi GBM Final Real-time Localization
- GRB 250901A: SVOM/VT optical afterglow with VHF data
- GRB 250901A: Swift-XRT afterglow detection
- EP250901a: Swift-XRT observations
- GRB 250901A: LCO optical upper limit
- EP250827b: Swift observations of AT 2025wkm
- GRB 250901A: SVOM detection of a burst
- GRB 250831B: SVOM/GRM observation
- GRB 250830C: Insight-HXMT detection
- GRB 250830C: GECAM-B detection
- GRB 250830C: AstroSat CZTI detection of a long burst
- EP250831a: EP-FXT follow-up observation
- EP250831a: Swift-XRT observations
- GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
- GRB 250831A: Swift-XRT counterpart detection
- GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250831A: SVOM/VT upper limit with VHF data
- GRB 250831A: SVOM detection of a soft burst
- GRB 250830B: Swift-XRT observations
- EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
- GRB 250830B: Swift ToO observations
- GRB 250830B: MAXI/GSC detection
- GRB 250830A / MAXI J0853+337: MAXI/GSC detection
- GRB 250828B: Swift-BAT refined analysis
- EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
- GRB 250808B: SVOM detection of a burst through offline search
- Swift GRB 250828B: Global MASTER-Net observations report