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"19936 results found.
- GRB 260925A: Swift-XRT refined Analysis
- Swift Trigger 1513439 is probably not a GRB
- GRB 260925A: Swift/UVOT Upper Limits
- Konus-Wind detection of GRB 260924A
- GRB 260922A: Glowbug gamma-ray detection
- GRB 260925A: Enhanced Swift-XRT position
- GRB 260925A: COLIBRÍ optical upper limits
- GRB 260925A: FRAM-Auger optical limit
- GRB 260924A: Ondrejov D50 optical afterglow detection
- GRB 260924A: SVOM/GRM observation
- GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
- GRB 260925A: Swift detection of a burst
- GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
- GRB 260924A: Swift/UVOT Detection
- GRB 260924A: Swift-BAT refined analysis
- GRB 260924A: NuSTAR detection of prompt emission
- GRB 260924A: Swift/UVOT Upper Limits
- GRB 260924A: Swift-XRT refined Analysis
- Konus-Wind detection of GRB 260922A
- GRB 260922A: NuSTAR detection of prompt emission
- GRB 260921A: NuSTAR detection of prompt emission
- GRB 260921A: SVOM/GRM observation
- GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
- GRB 260924A: Fermi GRB Observation
- Konus-Wind detection of GRB 260921A (possible merger-origin)
- GRB 260924A: Fermi-LAT detection of a bright burst
- GRB 260924A: AstroSat CZTI detection
- GRB 260924A: NOT optical counterpart confirmation
- GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
- GRB 260922A: CALET Gamma-Ray Burst Monitor detection
- GRB 260924A: Enhanced Swift-XRT position
- GRB 260924A: Swift detection of a burst
- Trigger_21914: Swift ToO observations
- GRB 260922A: Ondrejov D50 optical limit
- GRB 260922A: Swift-BAT refined analysis
- GRB 260922A: Swift/UVOT Upper Limits
- GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
- GRB 260922A: COLIBRÍ optical upper limits
- GRB 260922A: Swift-XRT refined Analysis
- GRB 260922A: Enhanced Swift-XRT position
- Fermi-LAT Gamma-ray Observations of IceCube-260805A
- GRB 260922A: SVOM/C-GFT optical upper limit
- GRB 260922A: Swift detection of a burst
- GRB 260921A: AstroSat CZTI detection
- GRB 260921A: Swift-BAT refined analysis
- GRB 260921A: Fermi GBM Observation
- Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
- Swift GRB 260921A: Global MASTER-Net observations report
- GRB 260921A: Swift detection of a burst
- GRB 260915A: VLT optical and near-infrared upper limits
- GRB 260915A: Swift-XRT afterglow detection
- GRB 260909A: Swift-XRT observations
- GRB 260915A: Swift ToO observations
- GRB 260909A: Swift ToO observations
- GRB 260903A: Swift-XRT observations
- GRB 260903A: Swift ToO observations
- NuSTAR 260828: a 1100s hard X-ray transient
- GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
- Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- AT2026nik: EP-FXT X-ray counterpart
- Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
- SVOM/GRM observation of a bright burst from SGR 1E1841-045
- IPN triangulation of a bright burst from SGR 1E1841-045
- EP260321a: Chandra X-ray Non-detection
- Swift BAT trigger 1500295: A solar flare
- Swift BAT trigger 1500287: A solar flare
- 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
- 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 260208B: EP-FXT observation
- GRB 260208B: SVOM/VT optical candidate
- 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 260206A: Swift-XRT observations
- GRB 260206A: Tiled Swift observations
- GRB 260204A: SVOM/VT confirms fading of the optical afterglow
- GRB 260204A: Swift-XRT observations
- GRB 260204A: SVOM/VT optical candidate
- GRB 251230A: MeerLICHT afterglow detection
- GRB 260127A: GECAM-B observation
- GRB 260127B: AstroSat CZTI detection
- IPN triangulation of GRB 260121A
- GRB 260127A: Swift-BAT refined analysis
- GRB 260127B: Swift-XRT observations