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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"- MAXI GRB260916.37: Global MASTER-Net observations report
- GRB 260915A: Swift ToO observations
- GRB 260915A: J-band upper limit by SYSU 80cm infrared telescope
- GRB 260915A: SVOM/C-GFT optical upper limits
- GRB 260915A: EP-FXT follow-up observation
- GRB 260915A: SVOM/VT refined early optical upper limits
- GRB 260915A: EP-FXT follow-up observation
- GRB 260915A: REM optical/NIR observations
- GRB 260914A: REM optical/NIR observations
- GRB 260914A: VLT/X-shooter observations and redshift confirmation
- GRB 260915A: SVOM/VT optical upper limits
- GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
- GRB 260915A: 10.4m GTC deep optical limits
- GRB 260915A: NOT optical upper limit
- SVOM GRB260915.05: Global MASTER-Net observations report
- GRB 260915A: SVOM/VT optical upper limits from VHF data
- Fermi GBM Sub-Threshold Detection of GRB 260915A
- GRB 260915A: LCO optical upper limits
- EP Alert 260914.53: Global MASTER-Net observations report
- GRB 260914A: EP-FXT follow-up observation
- GRB 260915A: SVOM detection of a burst
- Fermi GBM Sub-Threshold Detection of GRB 260914A
- GRB 260914A: LCO optical observation
- GRB 260914A: SVOM/C-GFT optical observations
- GRB 260914A: SVOM/VT optical counterpart confirmation
- GRB 260914A: SVOM/VT optical observation from VHF data
- GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
- SVOM GRB260914.47: Global MASTER-Net observations report
- GRB 260914A: SVOM detection of a burst
- GRB 260913A: SVOM trigger sb26091302 is not an astrophysical event
- GRB 260818A: Continued ATCA observations
- SVOM GRB260913.32: Global MASTER-Net observations report
- GRB 260913A: SVOM/C-GFT optical upper limit
- GRB 260913A: SVOM detection of a faint burst
- GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
- GRB 260907A: SVOM/GRM observation
- GRB 260909A: CrAO and AbAO optical upper limits
- GRB 260909A: SVOM/ECLAIRs refined analysis
- GRB 260910B: GOTO tentative optical counterpart candidates
- GRB 260909A: Swift ToO observations
- GRB 260910B: Fermi GBM Final Real-time Localization
- GRB 260909A: KAIT optical upper limit
- GRB 260903A: Swift-XRT observations
- EP260806a: VLA+ALMA radio detections
- GRB 260909A: OHP/T193 z-band upper limit
- GRB 260909A: VLT optical and near-infrared upper limits
- EP Alert 260909.53: Global MASTER-Net observations report
- GRB 260909A: EP-FXT follow-up observation
- GRB 260910A: Fermi GBM Final Real-time Localization
- EP260806a: NOEMA detection
- EP260623a: NOEMA detections
- GRB 260909A: SVOM/VT optical upper limits
- GRB 260909A: SVOM/GRM observation
- GRB 260909A: Mondy optical observations and afterglow candidate
- GRB 260909A: Xinglong 2.16m optical upper limit
- GRB 260909A: SVOM/C-GFT optical upper limit
- GRB 260909A: SVOM detection of a burst
- The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
- Fermi trigger No 810554827: Global MASTER-Net observations report
- EP Alert 260908.60: Global MASTER-Net observations report
- GRB 260907A: Glowbug gamma-ray detection of a likely short burst
- GRB 260903A: Swift ToO observations
- Fermi GRB 260907B: Global MASTER-Net observations report
- GRB 260903A: SAO RAS optical upper limit
- The EP-WXT trigger 01709305715 is likely a flaring star
- GRB 260907B: Fermi GBM Final Real-time Localization
- Fermi GRB 260907A: Global MASTER-Net observations report
- GRB 260907A: Fermi GBM Final Real-time Localization
- EP260903a: EP-FXT follow-up observation
- EP Alert 260905.11: Global MASTER-Net observations report
- The EP-WXT trigger 01709302592 is likely a flaring star
- GRB 260903A: J-band upper limit with WINTER
- EP Alert 260903.47: Global MASTER-Net observations report
- GRB 260903A: SVOM/ECLAIRs refined analysis
- GRB260903A: Liverpool Telescope optical observations
- GRB 260903A: SAO RAS optical observations
- GRB 260830A: GECAM-B detection of a burst
- EP260903a: EP-WXT detection of a fast X-ray transient
- EP Alert 260903.62: Global MASTER-Net observations report
- GRB 260830A: Insight-HXMT/HE detection
- GRB 260903A: EP-FXT follow-up observation
- GRB 260903A: OHP/T193 optical afterglow detection
- GRB 260903A: NOT optical observations and afterglow fading
- NuSTAR Transient 260828: SOAR Optical Upper Limits
- SVOM GRB260903A: Global MASTER-Net observations report
- GRB 260903A: LCO optical observations
- GRB 260903A: SVOM/VT optical candidate
- GRB 260903A: Retraction of optical counterpart of GCN 45501
- GRB 260831A: GECAM-B observation
- GRB 260903A: LCO optical counterpart detection
- GRB 260827A: Insight-HXMT/HE detection
- GRB 260903A: SVOM detection of a soft faint burst
- EP260901a: SVOM/VT optical upper limits
- EP260901a: EP-FXT follow-up observation
- Konus-Wind detection of GRB 260829A
- GRB 260829A: SVOM/GRM observation
- GRB 260818A: ATCA detection of a candidate radio counterpart
- EP260830a: EP-FXT follow-up observation
- EP260901a: Global MASTER-Net observations report