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.
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"26037 results found.
- GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
- GRB 260310A/AT 2026fgk: WINTER NIR Detections
- GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
- Swift BAT trigger 1500295: A solar flare
- Swift BAT trigger 1500287: A solar flare
- GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
- GRB260310A / AT2026fgk: P200 Spectroscopy
- Swift BAT trigger 1500148: A solar flare
- Retraction of GCN 43965: GRB is actually solar flare
- GRB 260312A: Swift detection of a burst
- GRB 260208A: radio detection with the VLA
- GRB 260211A: late-time NOT i-band observations consistent with archival flux
- EP260302a: Optical afterglow rebrightening
- GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
- GRB 260303A: SVOM/VT optical observations
- EP260227A: 3.6m DOT optical afterglow detection
- EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
- GRB 260223A: 7DT detection and Medium-band SED of Afterglow
- GRB 260223A: COLIBRÍ optical afterglow decay confirmation
- IPN triangulation of GRB 260212A
- GRB 260206A: probable hard X-ray burst from 4U 0513-40
- Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
- GRB 260208A: Swift UVOT detection
- GRB 260208A: LCO detection of the optical counterpart
- GRB 260208B: refined analysis of the EP-FXT observation
- GRB 260204A: Swift-XRT afterglow detection
- GRB 260208A: Fermi GBM Observation
- GRB 260208B: Swift-XRT observations
- GRB 260204A: Swift/UVOT Upper Limits
- GRB 260208A: 1.3m DFOT optical detection
- GRB 260208B: EP-FXT observation
- GRB 260208B: SVOM/VT optical candidate
- GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
- GRB 260208A: SVOM/VT optical observation
- GRB 260208A: Swift-XRT observations
- GRB 260208B: Swift ToO observations
- GRB 260208B: Fermi-LAT detection
- GRB 260208A: Fermi-LAT detection
- GRB 260208A: Swift ToO observations
- GRB 260208A: Fermi GBM Classification Correction
- GRB 260206A: Swift-XRT observations
- EP260131a: VLA detection
- GRB 260206A: Tiled Swift observations
- GRB 260204A: SVOM/VT confirms fading of the optical afterglow
- GRB 260204A: Swift-XRT observations
- GRB 260204A: LCO optical afterglow detection
- GRB 260204A: SVOM/VT optical candidate
- GRB 260131A/B: OHP/T193 optical observations
- GRB 260131A: KAIT optical observations
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
- GRB 260131A/B: GTC/OSIRIS+ redshift confimation
- GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
- GRB 260131A/B: EP/FXT X-ray afterglow detection
- GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
- GRB 260127A: GECAM-B observation
- GRB 260131A: NOT spectroscopic redshift z = 1.434
- GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
- GRB 260127B: AstroSat CZTI detection
- EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
- EP260128a: J band upper limit by SYSU 80cm infrared telescope
- IPN triangulation of GRB 260121A
- GRB 260127A: Swift-BAT refined analysis
- GRB 260127B: Swift-XRT observations
- GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
- GRB 260127A: Fermi GBM Observation
- GRB 260127A: COLIBRÍ optical observations
- GRB 260127B: Swift ToO observations
- GRB 260127A : MITSuME Akeno optical afterglow candidate detection
- GRB 260127A: Swift-XRT refined Analysis
- GRB 260127A: SVOM/C-GFT optical observations
- GRB 260127A: Enhanced Swift-XRT position
- GRB 260127A: Prompt enhanced Swift-XRT position
- Swift GRB 260127A: Global MASTER-Net observations report
- GRB 260127A: LCO optical afterglow discovery
- GRB 260127A: Swift detection of a burst
- GRB 260125A: Swift-XRT observations
- Konus-Wind detection of GRB 260120B
- GRB 260125A: Swift ToO observations
- GRB 260114A: SVOM/VT optical upper limits
- GRB 260122B: Swift-BAT refined analysis
- GRB 260120B: SVOM/GRM observation
- GRB 260120B: AstroSat CZTI detection
- GRB 260114A: Insight-HXMT/HE detection
- GRB 260122B: Swift detection of a burst
- Swift GRB260122.97: Global MASTER-Net observations report
- GRB 260120B: Swift-BAT refined analysis
- GRB 260120B: Swift-XRT refined Analysis
- GRB 260120B: Fermi GBM Observation
- GRB 260120B: Swift/UVOT Detection
- GRB 260120B: COLIBRÍ optical upper limits
- GRB 260120B: Enhanced Swift-XRT position
- GRB 260120B: SVOM/C-GFT optical counterpart detection
- GRB 260101A: 239Alferov CubeSat detection
- GRB 260120B: Swift detection of a burst
- Swift GRB260120B: Global MASTER-Net observations report
- EP260119A: Mondy I-Band Observations
- GRB 260114A: Swift/UVOT Upper Limits
- Trigger 1442421: Swift detection of HMXB 1A 1118-61
- EP260119a: KAIT optical observations