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"27779 results found.
- EP260416a: Einstein Probe detection of an X-ray transient
- GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
- GRB 260415B: NuSTAR detection of long prompt emission
- GRB 260415B: Fermi GBM Final Localization
- GRB 260415A: Fermi GBM Final Real-time Localization
- GRB 260414A: Glowbug gamma-ray detection
- GRB 260412A: Insight-HXMT/HE detection
- GRB 260414A: Fermi GBM Final Real-time Localization
- GRB 260410A: Glowbug gamma-ray detection of a short burst
- GRB 260413A: Fermi GBM Final Real-time Localization
- GRB 260410B: Insight-HXMT/HE detection
- GRB 260410A: Insight-HXMT/HE detection
- Konus-Wind detection of GRB 260410A (short/hard)
- GRB 260410A: CALET Gamma-Ray Burst Monitor detection
- GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
- GRB 260411B: Fermi-LAT detection
- GRB 260412A: SVOM detection of a long burst
- GRB 260412A: Fermi GBM Final Real-time Localization
- GRB 260411B: COLIBRÍ optical observations
- GRB 260411B: Ondrejov D50 optical afterglow detection
- GRB260411B: 3.6m DOT optical observation
- GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
- GRB 260409A: Insight-HXMT/HE detection
- GRB 260411B: Fermi GBM Detection
- EP260409a: Gemini/FLAMINGOS2 J-band counterpart
- GRB 260411B: Fermi GBM Final Real-time Localization
- GRB 260411A: Fermi GBM Final Real-time Localization
- EP-WXT01709259790: Optical Upper limits with kinder observations
- GRB 260410B: SVOM/GRM detection of a short faint burst
- GRB 260410B: Fermi GBM Final Real-time Localization
- EP-WXT01709259790: Xinglong optical upper limit
- GRB 260410A: Fermi-LAT detection
- GRB 260410A: Fermi GBM Final Real-time Localization
- EP260321a: Chandra X-ray Non-detection
- GRB 260409A: Fermi GBM Final Real-time Localization
- GRB 260407A: GECAM-A detection
- GRB 260407A: Insight-HXMT/HE detection
- EP260409a: SVOM/VT optical upper limits
- GRB 260407A: CALET Gamma-Ray Burst Monitor detection
- EP260409a: Einstein Probe detection of an X-ray transient
- EP260321a: VLA radio detection
- GRB 260404A: Fermi GBM Final Localization
- GRB 260407A: Glowbug gamma-ray detection
- GRB 260310A / AT2026fgk: X-ray rebrightening
- EP260402a / GRB 260402A: Mephisto optical upper limits
- EP-WXT01709259586: Xinglong optical upper limit
- EP260403a: Mephisto optical upper limits
- EP260402a/GRB 260402A: Xinglong optical upper limit
- EP260321a: Upper limits from VLA radio observations
- GRID detection of GRB 260401A
- GRB 260407A: Fermi GBM Final Real-time Localization
- EP260405a: Einstein Probe detection of a fast X-ray transient
- GRB 260330B: SVOM/VT further optical observation
- EP260403a: LCO optical counterpart detection
- GRB 260330B: SVOM/VT optical candidate
- EP260403a: Einstein Probe detection of an X-ray transient
- GRB 260403A: AstroSat CZTI detection
- GRB 260402C: NuSTAR detection of prompt emission
- GRB 260402C: AstroSat CZTI detection of a long burst
- GRB 260403A: Fermi GBM Final Real-time Localization
- GRB 260402B: Fermi GBM Final Real-time Localization
- GRB 260402A / EP260402a: SVOM/VT optical upper limits
- EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
- GRB 260402A: SVOM detection of a burst
- GRB 260401A: NuSTAR detection of prompt emission
- GRB 260401A: CALET Gamma-Ray Burst Monitor detection
- GRB 260401A: MAXI/GSC detection
- GRB 260401A: Fermi GBM Final Real-time Localization
- EP260327a: Xinglong optical upper limit
- EP260329b: GOTO detection of optical counterpart
- GRB 260330B: SVOM/VT optical upper limits
- Konus-Wind detection of GRB 260320A
- Konus-Wind detection of GRB 260316B (duplicate submission)
- Konus-Wind detection of GRB 260316B
- GRB 260321A: SVOM/ECLAIRs refined analysis
- GRB 260330A: Glowbug gamma-ray detection
- Fermi GBM Sub-Threshold Detection of GRB 260330B
- GRB 260330B: SVOM detection of a burst
- EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
- EP260329a: COLIBRÍ optical upper limit
- GRB 260330A: Fermi GBM Final Real-time Localization
- GRB 260327A: Insight-HXMT/HE detection
- EP260329b: Optical follow-up with Kinder observations
- EP260329a: Optical upper limit with Kinder observations
- GRB 260326A: Insight-HXMT/HE detection
- EP260329b: Einstein Probe detection of an X-ray transient
- EP260329a: Einstein Probe detection of an X-ray transient
- EP-WXT trigger 01709259209: TRT optical counterpart detection
- GRID detection of GRB 260326A
- EP260327a: SVOM/VT optical upper limits
- SMA Detection of GRB 260310A / AT 2026fgk
- GRB 260327A: AstroSat CZTI detection of a long burst
- EP260327a: Einstein Probe detection of an X-ray transient
- GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
- GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
- IPN triangulation of GRB 260320A
- EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
- GRB 260326A: Fermi GBM Detection
- GRB 260325A: Fermi GBM Final Localization
- GRB 260326A: Fermi GBM Final Real-time Localization