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"6759 results found.
- GRB 260818B: Further EP-FXT observation
- GRB 260808B: SAO RAS observations of the optical rebrightening
- GRB 260807A: EP-FXT follow-up observations
- GRB 260822A: EP/FXT follow-up observations
- GRB 260822A: GROWTH-India Telescope Upper Limits
- Fermi-LAT Gamma-ray Observations of IceCube-260821A
- Fermi-LAT Gamma-ray Observations of IceCube-260807A
- GRB 260818B: EP-FXT follow-up observation
- GRB260818A: EP-FXT follow-up observation
- EP260806a: SAO RAS multicolor optical observations
- EP260812b: Optical upper limit with Kinder
- EP260812a: NOT and Liverpool Telescope upper limits:
- GRB 260809A: SAO RAS optical observations
- GRB 260808B: SAO RAS optical observations
- 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
- Fermi-LAT Gamma-ray Observations of IceCube-260722A
- EP260727a: SAO RAS optical observations
- EP260728a: EP-FXT follow-up observation
- GRB 260726A: EP-FXT follow-up observations
- GRB 260726A: Fermi GBM Observation
- Konus-Wind detection of GRB 260727A
- 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 260718A: Fermi GBM Observation
- GRB 260310A / AT2026fgk: Late-time Chandra Detection
- GRB 260618B: EP-FXT follow-up observation upper limit
- GRB 260714B: Fermi-LAT detection
- GRB 260714B: Fermi GBM Detection
- GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
- EP260711a: EP-FXT follow-up observation
- Fermi-LAT Gamma-ray Observations of IceCube-260712A
- Fermi-LAT Gamma-ray Observations of IceCube-260708A
- Fermi-LAT Gamma-ray Observations of IceCube-260704A
- GRB 260710A: Fermi GBM Detection
- GRB 260708A: Fermi-GBM observation
- GRB 260708A: Fermi-LAT detection
- GRB 260706A: Further EP-FXT follow-up observation
- GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
- GRB 260706A: EP-FXT follow-up observation
- GRB 260706A: Fermi GBM 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
- Fermi-LAT Gamma-ray Observations of IceCube-260622A
- EP260628a: EP-FXT follow-up observation
- EP260626a: EP-FXT follow-up observation
- Konus-Wind detection of GRB 260623B / EP260623a
- GRB 260618A: Fermi GBM Observation
- EP260623a: Optical follow-up observations with Kinder
- GRB 260614B: EP-FXT follow-up observation
- GRB 260618B: Fermi GBM Observation
- Fermi-LAT Gamma-ray Observations of IceCube-260610A
- GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
- EP260618a: EP-FXT follow-up observation
- GRB 260618B: Fermi-LAT detection
- EP260618a: EP-WXT detection of an X-ray transient
- EP260616a/GRB 260616B: EP-FXT follow-up observation
- GRB 260617A: Fermi GBM Detection
- GRB 260616A: Fermi GBM Observation
- GRB 260616A: Fermi-LAT detection
- GRB 260616B: Fermi GBM Detection
- GRB 260614B: Fermi GBM Observation
- GRB 260610B: Fermi GBM Observation
- GRB 260610B / AT2026owq: further SAO RAS optical observations
- IceCube-260610A: EP-FXT follow-up observation
- GRB 260610B / AT2026owq: OASDG optical observations
- GRB 260610B / AT2026owq: SAO RAS optical observations
- EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260608A: Fermi GRB Observation
- GRB 260604C: further SAO RAS optical observations
- EP260605a: EP-FXT follow-up observation
- GRB 260607B: Fermi GBM Observation
- GRB 260607B: Fermi-LAT detection
- GRB 260604C: SAO RAS optical observations
- EP260602d: EP-FXT follow-up observation
- EP260602c: EP-FXT follow-up observation
- GRB 260604C: Fermi GBM Observation
- EP260602a: EP-FXT follow-up observation
- EP260602d: Optical Upper limits with kinder observations
- GRB 260603A: EP-FXT follow-up observation
- EP260601a/GRB 260601B: EP-FXT follow-up observation
- EP260602b: EP-FXT follow-up observation
- EP260602a: Optical upper limits with Kinder observations
- GRB 260601A: Fermi GBM Observation
- AT2026nik: EP-FXT X-ray counterpart
- EP260527a/GRB 260527A: EP-FXT follow-up observation
- EP260526a: EP-FXT follow-up observation
- GRB 260522A: Fermi GBM Observation
- GRB 260522A: Fermi-LAT detection
- Konus-Wind detection of GRB 260515A
- GRB 260515A: EP-FXT follow-up observation
- EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260515A: NOT optical observations.