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"26496 results found.
- GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
- The EP-WXT trigger 01709266798 is likely a flaring star
- GRB 260604C: Jinshan optical observations
- GRB 260604C: Fermi GBM Observation
- EP260602d: J-band upper limit with WINTER
- EP260602b: J-band upper limit with WINTER
- GRB 260604C: LAST detection of optical counterpart candidate
- GRB 260604C: SVOM detection of a long burst
- GRB 260603A: Simeiz Zeiss-1000 optical upper limit
- EP260602a: EP-FXT follow-up observation
- EP260603a: Einstein Probe detection of a fast X-ray transient
- EP260602d: Optical Upper limits with kinder observations
- EP260602b: Liverpool Telescope observations
- EP260602a: Liverpool Telescope optical upper limits
- EP260602b: Liverpool Telescope and LCO observations
- EP260602a: GTC and Liverpool Telescope optical observations
- GRB 260603A: EP-FXT follow-up observation
- EP260601a/GRB 260601B: EP-FXT follow-up observation
- GRB 260601B / EP260601a: Mondy optical upper limit
- EP260602b: EP-FXT follow-up observation
- GRB 260601B/EP260601a: Glowbug gamma-ray detection
- GRB 260603A: Kilonova-Catcher optical upper limit
- GRB 260603A: SVOM/VT optical observations
- EP260602a: NOT NIR J-band observations
- GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
- EP260602d: Einstein Probe detection of a fast X-ray transient
- GRB 260601A: SVOM/GRM observation of a short burst
- EP260602c: Einstein Probe detection of a fast X-ray transient
- GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
- EP260602a: COLIBRÍ optical observations
- GRB260601B/EP260601a: NOT near-infrared observations
- GRB 260603A: SVOM detection of a burst
- EP260602b: Einstein Probe detection of a fast X-ray transient
- EP260602a: SVOM/VT optical candidate
- EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
- GRB 260601B/EP260601a: J-band upper limit with WINTER
- EP260530a/AT 2026nwl: COLIBRÍ optical follow up
- EP260530a/AT 2026nwl: KAIT optical observations
- GRB 260602A: Fermi GBM Final Real-time Localization
- EP260602a: Optical upper limits with Kinder observations
- EP260602a: Einstein Probe detection of a fast X-ray transient
- GRB 260601B/EP260601a: SVOM/VT optical observations
- GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
- EP260601a: Einstein Probe detection of an X-ray transient
- EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
- 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 260601A: Fermi GBM Observation
- EP260530a/AT 2026nwl: COLIBRÍ optical observations
- GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
- GRB 260527A/EP260527a: Glowbug gamma-ray detection
- GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
- The EP-WXT trigger 01709266272 is likely a flaring star
- AT2026nik: EP-FXT X-ray counterpart
- AT 2026nuz: COLIBRÍ optical observations
- EP260527a/GRB 260527A: optical upper limit with Kinder observations
- GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
- GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
- EP260526a: SVOM/VT optical upper limits
- EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
- EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
- EP260527a/GRB 260527A: EP-FXT follow-up observation
- Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
- EP260526a: EP-FXT follow-up observation
- EP260527a: SVOM/VT optical observation
- EP260527a: COLIBRÍ optical detection
- EP260527a: Einstein Probe detection of a fast X-ray transient
- The EP-WXT trigger 01709266172 is likely a flaring star
- The EP-WXT trigger 01709266147 is likely a flaring star
- EP260526a: LCO optical upper limits
- EP260526a: Einstein Probe detection of a fast X-ray transient
- GRB 260525A: AstroSat CZTI detection
- EP260526.405: COLIBRÍ optical upper limits
- The EP-WXT trigger 01709266106 is not a real source
- EP01709266106 (EP260526a?): Liverpool Telescope upper limits
- EP-WXT 01709266106: NOT optical upper limits
- GRB 260522A: Fermi GBM Observation
- EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
- EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
- GRB 260519C: SVOM/GRM observation
- GRB 260511A: iTelescope T-75 optical detection
- GRB 260520B: SVOM/GRM observation
- Konus-Wind detection of GRB 260519C
- GRB 260509A: SVOM/ECLAIRs refined analysis
- Konus-Wind detection of GRB 260518A
- GRB 260518A: AstroSat CZTI detection of a long burst
- GRB 260421B: radio detection with the VLA
- GRB 260509A: CrAO ZTSh optical upper limit
- GRB 260516D: EP-FXT follow-up observation
- GRB 260516D: GOTO optical counterpart detection
- GRB 260516D: LCO optical observations
- GRB 260515A: further Liverpool Telescope observations
- GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
- GRB 260516D: GROWTH-India Telescope optical detection
- GRB 260516D: SVOM/VT optical bright candidate
- GRB 260515A: CrAO ZTSh BVRI optical observations
- GRB 260516D: SVOM possible detection of a burst
- Konus-Wind detection of GRB 260515A
- GRB 260515A: LCO optical counterpart detection