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"3388 results found.
- GRB 260818B: Further EP-FXT observation
- GRB 260807A: EP-FXT follow-up observations
- GRB 260822A: EP/FXT follow-up observations
- GRB 260818B: EP-FXT follow-up observation
- GRB260818A: EP-FXT follow-up observation
- GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
- GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
- AT 2026wki: EP/FXT follow-up observations
- GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
- GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
- EP260728a: EP-FXT follow-up observation
- GRB 260726A: EP-FXT follow-up observations
- GRB 260727A: EP/FXT follow-up observations
- EP260723a: further EP-FXT follow-up observation
- EP260725a: EP-WXT detection of an X-ray transient
- EP260723a: EP-FXT follow-up observation
- GRB 260718A: EP-FXT follow-up observation
- GRB 260310A / AT2026fgk: Late-time Chandra Detection
- GRB 260618B: EP-FXT follow-up observation upper limit
- GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
- EP260711a: EP-FXT follow-up observation
- Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
- GRB 260706A: Further EP-FXT follow-up observation
- GRB 260706A: EP-FXT follow-up observation
- GRB 260704A: EP-FXT follow-up observation
- EP260703a: EP-FXT follow-up observation
- EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
- EP260628a: EP-FXT follow-up observation
- EP260626a: EP-FXT follow-up observation
- GRB 260614B: EP-FXT follow-up observation
- EP260618a: EP-FXT follow-up observation
- EP260618a: EP-WXT detection of an X-ray transient
- EP260616a/GRB 260616B: EP-FXT follow-up observation
- IceCube-260610A: EP-FXT follow-up observation
- EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260605a: EP-FXT follow-up observation
- GRB 260607B: Fermi-LAT detection
- EP260602d: EP-FXT follow-up observation
- EP260602c: EP-FXT follow-up observation
- EP260602a: EP-FXT follow-up observation
- GRB 260603A: EP-FXT follow-up observation
- EP260601a/GRB 260601B: EP-FXT follow-up observation
- EP260602b: EP-FXT follow-up observation
- AT2026nik: EP-FXT X-ray counterpart
- EP260527a/GRB 260527A: EP-FXT follow-up observation
- EP260526a: EP-FXT follow-up observation
- Fermi GRB 260516C: Global MASTER-Net observations report
- GRB 260515A: EP-FXT follow-up observation
- EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
- EP260512a: EP-FXT follow-up observation
- GRB 260511B: EP-FXT follow-up observation
- GRB 260510B: EP-FXT follow-up observation
- SVOM GRB 260509A: MASTER-OAFA optical observation
- SVOM GRB 260504B: MASTER-OAFA optical observations
- EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260310A: Late-time Chandra X-ray Detection
- EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
- EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- GOTO26djh/AT2026jpw : MASTER OT observation
- GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
- GRB 260411B: Fermi GBM Detection
- EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- EP260321a: Chandra X-ray Non-detection
- EP260405a: Global MASTER-Net observations report
- EP260403a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260402A: MASTER optical observations
- EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
- GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
- EP260316a: refined analysis of the EP-WXT and EP-FXT observations
- IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
- GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
- GRB 260226A: Fermi-LAT refined analysis
- EP260223a: EP-FXT follow-up observation
- EP260214b: EP-FXT follow-up observation
- EP260214a: refined analysis of the EP-FXT observation
- EP260213a: refined analysis of the EP-FXT observation
- GRB 260208A: Swift UVOT detection
- EP260210a: refined analysis of the EP-FXT observation
- GRB 260208B: refined analysis of the EP-FXT observation
- GRB 260204A: Swift-XRT afterglow detection
- GRB 260208B: Swift-XRT observations
- GRB 260204A: Swift/UVOT Upper Limits
- GRB 260208A: Swift-XRT observations
- GRB 260208B: Fermi-LAT detection
- GRB 260206A: Swift-XRT observations
- GRB 260204A: Swift-XRT observations
- EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
- GRB 260127B: Swift-XRT observations
- GRB 260127A: Swift-XRT refined Analysis
- GRB 260127A: Prompt enhanced Swift-XRT position
- GRB 260125A: Swift-XRT observations
- EP260126a: EP-FXT follow-up observation
- GRB 260120B: Swift-XRT refined Analysis
- EP260119a: update of EP-FXT follow-up observation
- GRB 260117A: Swift-XRT afterglow detection
- Swift GRB260118.48: Global MASTER-Net observations report
- GRB 260117A: Swift-XRT observations
- GRB 260114A: VLT/HAWK-I near-infrared upper limits