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"27001 results found.
- GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
- EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
- Fermi GRB 260323A: Global MASTER-Net observations report
- GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
- GRB 260320A: Glowbug gamma-ray detection
- EP260321a: COLIBRÍ further optical observations and brightening
- EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
- EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
- GRB 260321A: EP-FXT follow-up observation
- EP260321a: GOTO detection of blue variable source
- EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
- EP260321a: further Kinder optical observations
- GRB 260321A: SVOM/VT optical upper limits
- EP260321a: Las Cumbres upper limit
- GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
- EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
- EP260321a: SVOM/VT optical upper limit
- Fermi GBM Sub-Threshold Detection of GRB 260321A
- EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
- EP260321a: Global MASTER-Net observations report
- EP260321a: Einstein Probe detection of an X-ray transient
- GRB 260318A: Glowbug gamma-ray detection
- GRB 260310A / AT 2026fgk: KAIT optical observations
- GRB 260320A: NuSTAR detection of prompt emission
- EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
- GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
- GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
- EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
- GRB 260318A: SVOM/GRM observation
- GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
- GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
- Fermi GRB 260318A: Global MASTER-Net observations report
- GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
- GRB 260310A / AT 2026fgk: radio detection with the VLA
- GRB 260310A / AT2026fgk: SVOM/VT optical observations
- GRB 260310A / AT2026fgk: LCO optical observations
- GRB 260316B: SVOM/GRM observation
- EP260316a / GRB 260316A: SVOM/VT optical upper limits
- EP260316a: COLIBRÍ faint optical counterpart candidate
- Fermi-LAT Gamma-ray Observations of IceCube-260315A
- EP260316a: refined analysis of the EP-WXT and EP-FXT observations
- IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
- EP260316a: Xinglong optical upper limit
- EP260316a: optical upper limit with Kinder observations
- EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
- GRB 260314A: Glowbug gamma-ray detection
- The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
- IceCube-260315A: COLIBRÍ optical observations
- EP260314a: Xinglong optical upper limit
- EP260314a: optical upper limit with Kinder observations
- IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
- GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
- GRB 260310A / AT 2026fgk: iTelescope optical observations
- EP260314a: COLIBRÍ optical upper limit
- EP260314a: refined analysis of the EP-WXT and EP-FXT observations
- EP260314a: Global MASTER-Net observations report
- EP260314a: SVOM/VT optical candidate
- Fermi trigger No 795185313: Global MASTER-Net observations report
- IceCube Alert 260315A: Global MASTER-Net observations report
- EP260314a: Einstein Probe detection of an X-ray transient
- GRB 260310A / AT2026fgk: SAO RAS optical observations
- GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
- GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
- Fermi GRB 260314A: Global MASTER-Net observations report
- Fermi GRB 260313A: Global MASTER-Net observations report
- GRB 260310A/AT 2026fgk: WINTER NIR Detections
- GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
- GRB 260310A/AT 2026fgk: DDOTI Optical Detection
- GRB 260312B: AstroSat CZTI detection
- GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
- GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
- GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
- GRB 260312B: Glowbug gamma-ray detection
- GRB 260310A: Fermi GBM Observation
- GRB 260310A: potential optical counterpart
- Fermi GRB 260312B: Global MASTER-Net observations report
- Fermi GRB 260311B: Global MASTER-Net observations report
- GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
- GRB 260131A/B: radio detection with the VLA
- EP260302a: MeerKAT radio counterpart
- GRB 260308A: SVOM/GRM observation of a short GRB
- EP260306a: Mondy optical upper limit
- Fermi GRB 260310B: Global MASTER-Net observations report
- Fermi GRB 260310A: Global MASTER-Net observations report
- GRB 260208A: radio detection with the VLA
- GRB 260307A: Glowbug gamma-ray detection
- Fermi GBM Sub-Threshold Detection of GRB 260307B
- GRB 260307B: Mephisto optical upper limits
- GRB 260307B: possible NOT optical counterpart
- GRB 260307B: SVOM/VT upper limit with X band data analysis
- Fermi GRB 260307A: Global MASTER-Net observations report
- GRB260307B: GROWTH-India Telescope optical upper limit
- GRB 260307B: SVOM/VT optical candidate
- GRB 260307B: SVOM/C-GFT upper limit
- GRB 260307B: SVOM detection of a burst
- EP260306a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260207A: TESS Detection and Possible VLA Counterpart
- EP260302a: SVOM/VT optical observation
- EP260306a: Gemini-North redshift z = 4.773