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"3089 results found.
- GRB 260818B: Further EP-FXT observation
- The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
- IceCube-260825A: No transient candidates from the Zwicky Transient Facility
- IceCube Alert 260825A: Global MASTER-Net observations report
- GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
- EP260806a: SAO RAS multicolor optical observations
- GRB 260813A: Fermi GBM Final Real-time Localization
- GRB 260808B: SAO RAS optical observations
- GRB 260809A: NOT optical observations
- GRB 260809A: SVOM/VT optical counterpart
- IceCube-260805A: One candidate from the Zwicky Transient Facility
- GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- Fermi GRB 260805A: Global MASTER-Net observations report
- Fermi GRB 260802B: Global MASTER-Net observations report
- The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
- EP260729a: Einstein Probe detection of an X-ray transient
- GRB 260726A: SVOM/VT optical candidate
- GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
- GRB 260727A: GOTO early optical upper limit
- Fermi GRB 260726A: Global MASTER-Net observations report
- EP260723a: further EP-FXT follow-up observation
- IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
- GRB 260718A : GRANDMA and KNC upper limits
- IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
- GRB 260714B: Fermi GBM Detection
- IceCube-260708A: One candidate from the Zwicky Transient Facility
- GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- IceCube-260704A: No candidates from the Zwicky Transient Facility
- IPN triangulation of GRB 260627A
- Fermi GRB 260703A: Global MASTER-Net observations report
- GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
- Fermi trigger No 804552016: Global MASTER-Net observations report
- Konus-Wind detection of GRB 260623B / EP260623a
- EP260618a: EP-FXT follow-up observation
- GRB 260616C: GECAM-B observation of a burst
- GRB 260617A: Fermi GBM Detection
- GRB260616C: MAXI/GSC detection
- GRB 260614B: SVOM detection of a burst
- IceCube-260610A: No candidates from the Zwicky Transient Facility
- EP260610b: SVOM/VT optical confirmation with blue color
- EP260610a: SVOM/VT optical upper limits
- GRB 260608C: Fermi GBM Final Real-time Localization
- GRB 260607B: Fermi GBM Observation
- GRB 260604C: LAST detection of optical counterpart candidate
- EP260602a: EP-FXT follow-up observation
- EP260601a/GRB 260601B: EP-FXT follow-up observation
- Fermi GRB 260602B: Global MASTER-Net observations report
- Fermi GRB 260602B: Global MASTER-Net observations report
- GRB 260601A: Fermi GBM Observation
- Fermi trigger No 801900520: Global MASTER-Net observations report
- GRB 260531A: MAXI/GSC detection
- EP260527a/GRB 260527A: further FTW optical and NIR observations
- GRB 260527A / EP260527a: VLA radio detection
- GRB 260523A: Fermi GBM Final Real-time Localization
- Fermi GRB 260516C: Global MASTER-Net observations report
- GRB 260516B: Fermi GBM Final Real-time Localization
- SVOM GRB 260515A: Global MASTER-Net observations report
- SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
- IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
- EP260514a: Global MASTER-Net observations report
- GRB 260511B: Mephisto multi-band optical followup
- GRB 260511B: LCO optical counterpart detection
- GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
- EP260509a: LCO optical upper limits
- GRB 260510C: SVOM/VT optical upper limits
- SVOM GRB 260509A: MASTER-OAFA optical observation
- GRB 260509A: SVOM/VT optical candidate with VHF data
- GRB 260509A: GOTO optical counterpart candidate
- EP260507a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
- EP260507a: Kinder optical counterpart candidate
- EP260507a: LCO optical counterpart
- EP260507a: Einstein Probe detection of an X-ray transient
- Fermi GRB 260506A: Global MASTER-Net observations report
- GRB 260430B: AstroSat CZTI detection of a long burst
- SVOM GRB 260504B: MASTER-OAFA optical observations
- EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
- GRB 260429B / EP260429a: COLIBRÍ optical upper limit
- GRB 260429A: Fermi GBM Detection
- Fermi GRB 260429A: Global MASTER-Net observations report
- EP260430a: Global MASTER-Net observations report
- EP260430a: Einstein Probe detection of an X-ray transient
- EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
- IPN triangulation of GRB 260424B (short)
- IceCube Alert 260425A: Global MASTER-Net observations report
- GRB 260419A: AstroSat CZTI detection
- GRB 260310A: Late-time Chandra X-ray Detection
- Fermi GRB 260421B: Global MASTER-Net observations report
- Fermi GRB 260421A: Global MASTER-Net observations report
- GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
- GRB 260419B: Fermi GBM Final Real-time Localization
- Fermi GRB 260417A: Global MASTER-Net observations report
- EP260416a: WFST optical observations and rebrightening
- COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
- EP260416a: Global MASTER-Net observations report
- EP260321a: CMO SAI J,K observations
- GRB 260414A: Fermi GBM Final Real-time Localization
- Fermi GRB 260412A: Global MASTER-Net observations report
- GRB 260410B: Fermi GBM Observation
- GRB 260411B: Fermi GBM Final Real-time Localization