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"28096 results found.
- GRB 260604C: SVOM detection of a long burst
- GRB 260604C: Fermi GBM Final Real-time Localization
- GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
- GRB 260603A: NOT optical observations
- GRB 260603A: Simeiz Zeiss-1000 optical upper limit
- GRB 260604B: Fermi GBM Final Real-time Localization
- GRB 260601A: CALET Gamma-Ray Burst Monitor detection
- EP260602a: EP-FXT follow-up observation
- EP260603a: Einstein Probe detection of a fast X-ray transient
- EP260602d: Optical Upper limits with kinder observations
- GRB 260604A: Fermi GBM Final Real-time Localization
- EP260602b: Liverpool Telescope observations
- GRB 260603B: Fermi GBM Final Localization
- Konus-Wind detection of GRB 260601B/EP260601a
- EP260602b: EP-FXT follow-up observation
- GRB 260601B/EP260601a: Glowbug gamma-ray detection
- EP260602d: Einstein Probe detection of a fast X-ray transient
- EP260602c: Einstein Probe detection of a fast X-ray transient
- EP260602a: COLIBRÍ optical observations
- GRB 260603A: SVOM detection of a burst
- EP260602b: Einstein Probe detection of a fast X-ray transient
- GRB 260601B/EP260601a: Insight-HXMT detection
- EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
- GRB 260602B: Fermi GBM Final Localization
- GRB 260602A: Fermi GBM Final Real-time Localization
- GRB 260601B: CALET Gamma-Ray Burst Monitor detection
- EP260602a: Optical upper limits with Kinder observations
- GRB 260601B / EP260601a: NuSTAR detection of prompt emission
- EP260602a: Einstein Probe detection of a fast X-ray transient
- GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
- EP260601a: Einstein Probe detection of an X-ray transient
- EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
- GRB 260601A: Glowbug gamma-ray detection of a short burst
- GRB 260531B: Glowbug gamma-ray detection
- GRB 260516D: VLA radio detection
- GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
- GRB 260527A/EP260527a: Glowbug gamma-ray detection
- GRB 260601A: Fermi GBM Final Real-time Localization
- GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
- GRB 260531C: Fermi GBM Final Localization Correction
- AT2026nik: EP-FXT X-ray counterpart
- GRB 260531B: Fermi GBM Final Real-time Localization
- GRB 260531A: MAXI/GSC detection
- AT 2026nuz: COLIBRÍ optical observations
- IPN triangulation of GRB 260527A / EP260527a
- GRB 260530B: SVOM/GRM detection of a possible bright short GRB
- GRB 260530A: Fermi GBM Final Real-time Localization
- GRB 260527A / EP260527a: VLA radio detection
- GRB 260529A: GOTO tentative optical afterglow candidate
- GRB 260527A/EP260527a: Insight-HXMT detection
- GRB 260529A: Fermi GBM Final Real-time Localization
- EP260526a: SVOM/VT optical upper limits
- EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
- EP260527a / GRB 260527A: NOT optical observations
- GRB 260527A/EP260527a: FTW optical and NIR observations
- GRB 260527A: CALET Gamma-Ray Burst Monitor detection
- EP260527a/GRB 260527A: EP-FXT follow-up observation
- GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
- Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
- EP260526a: EP-FXT follow-up observation
- EP260527a: COLIBRÍ optical detection
- EP260527a: Einstein Probe detection of a fast X-ray transient
- GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
- EP260526a: LCO optical upper limits
- EP260526a: Einstein Probe detection of a fast X-ray transient
- GRB 260525A: AstroSat CZTI detection
- GRB 260526A: Fermi GBM Final Real-time Localization
- EP01709266106 (EP260526a?): Liverpool Telescope upper limits
- GRB 260525A: Fermi GBM Final Real-time Localization
- GRB 260523B: AstroSat CZTI detection
- GRB 260523B: Fermi GBM Final Real-time Localization
- GRB 260523A: Fermi GBM Final Real-time Localization
- GRB 260522B: NuSTAR detection of prompt emission
- GRB 260522B: Fermi GBM Final Real-time Localization
- EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
- GRB 260522A: Fermi-LAT detection
- GRB 260522A: Fermi GBM Final Real-time Localization
- GRB 260511A: iTelescope T-75 optical detection
- GRB 260411B: TERI Gamma-ray detection
- GRB 260407A: TERI Gamma-ray detection
- GRB 260307A: TERI Gamma-ray detection
- GRB 260225D: TERI Gamma-ray detection
- GRB 251118A: TERI Gamma-ray detection
- GRB 251113A: TERI Gamma-ray detection
- GRB 260428A: TERI Gamma-ray detection
- Konus-Wind detection of GRB 260519C
- GRB 260520B: Fermi GBM Final Localization
- GRB 260520A: Fermi GBM Final Localization
- GRB 260519D: Fermi GBM Final Localization Correction
- GRB 260519C: NuSTAR detection of prompt emission
- Konus-Wind detection of GRB 260518A
- GRB 260519B: Fermi GBM Final Localization
- GRB 260519A: Fermi GBM Final Localization
- GRB 260518A: AstroSat CZTI detection of a long burst
- GRB 260421B: radio detection with the VLA
- GRID detection of GRB 260511A
- GRB 260516D: GOTO optical counterpart detection
- GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
- GRB 260516D: GROWTH-India Telescope optical detection