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"12316 results found.
- GRB 250506A: SVOM/VT optical upper limit
- IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250506A: Swift/UVOT Upper Limits
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250507A: SVOM/VT optical upper limit
- GRB 250506A: Swift-XRT observations
- Fermi-LAT Gamma-ray Observations of IceCube-250506A
- GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250506A: Mephisto optical upper limits
- GRB 250502A: Bassano Bresciano Observatory upper limit
- IceCube Alert 250506.59: Global MASTER-Net observations report
- GRB 250506A: Xinglong 2.16m optical upper limit
- SVOM/sb25050601: EP-FXT observations
- GRB 250506A: REM optical/NIR upper limits
- GRB 250506A: Swift XRT observations and possible counterpart detection
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
- GRB 250504A: VLT/X-shooter upper limits
- Fermi GRB 250505A: Global MASTER-Net observations report
- GRB 250504A: SVOM/VT upper limit
- Fermi GRB 250504A: Global MASTER-Net observations report
- GRB 250504A: Swift detection of a burst
- Swift GRB250504.98: Global MASTER-Net observations report
- Fermi trigger No 767975731: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250429A
- GRB 250430A: Swift/UVOT Detection
- Fermi GRB 250502B: Global MASTER-Net observations report
- GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
- GRB 250430A / EP250430a: J-band upper limits with WINTER
- EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
- GRB 250430A: Leavitt Observatory optical upper limit
- GRB 250430A: Bassano Bresciano Observatory upper limit
- GRB 250430A : MITSuME Akeno optical upper limits
- SVOM/sb25043004: EP-FXT observations
- IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250430A: Kanata optical upper limit
- Swift GRB250430.73: Global MASTER-Net observations report
- EP250428b: FTW optical and NIR observations
- Fermi trigger No 767623859: Global MASTER-Net observations report
- EP250428b: GROWTH-India telescope optical upper limit
- EP250428b: SVOM/VT upper limit
- EP250428b: SAO RAS optical upper limit
- EP250428b: LAST optical upper limit
- GRB 250427A: Swift/UVOT Detection
- EP250428b: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-250426A
- EP250427a: Global MASTER-Net observations report
- IceCube Alert 250426.74: Global MASTER-Net observations report
- IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
- IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250424A: Swift/UVOT Detection
- Fermi-LAT gamma-ray observations of IceCube-250421A
- GRB 250419a: Continued Liverpool Telescope observations
- GRB 250419A: Liverpool Telescope optical upper limit
- Swift GRB 250424A: Global MASTER-Net observations report
- Swift GRB 250424A: Global MASTER-Net OT detection
- EP250421a: Nickel optical upper limit
- EP250421a: Upper limits from Fermi-GBM Observations
- SVOM/sb25042207: XRT observations
- SVOM/sb25042207: BOOTES-2 early optical upper limit
- SVOM/sb25042207: GOTO optical upper limits
- GRB 250419A: Mephisto Multi-band Optical Detection
- EP250421a: REM optical upper limit
- EP250421A: COLIBRÍ Optical Upper Limit
- Fermi GRB 250421A: Global MASTER-Net observations report
- EP250421a: Global MASTER-Net observations report
- IceCube Alert 250421.71: Global MASTER-Net observations report
- IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250419A: MASTER optical afterglow observation
- Fermi-LAT Gamma-ray Observations of IceCube-250416A
- GRB 250419A: GOTO optical counterpart detection
- GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
- EP250416a: GSP optical upper limit
- EP250416a: Global MASTER-Net observations report
- IceCube-250416A: Global MASTER-Net observations report
- SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
- EP250304a: ATCA radio observations
- Fermi trigger No 766148493: Global MASTER-Net observations report
- Fermi trigger No 766173972: Global MASTER-Net observations report
- Fermi GRB 250411A: Global MASTER-Net observations report
- GRB 250314A: e-MERLIN observations
- EP250227a: Further NOT optical observations
- EP250407a: Global MASTER-Net observations report
- Fermi-LAT gamma-ray observations of IceCube-250406A
- EP250407a: Swift-XRT observations
- IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250407A: Swift-XRT afterglow detection
- Fermi GRB 250407A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
- IceCube 250406A: DDOTI Optical Observations of the Refined Position
- Konus-Wind detection of GRB 250406B (short/hard)
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- IceCube Alert 250406.95: Global MASTER-Net observations report
- Fermi trigger No 765663719: Global MASTER-Net observations report
- Fermi GRB 250406A: Global MASTER-Net observations report
- Fermi trigger No 765619921: Global MASTER-Net observations report
- GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
- Konus-Wind detection of GRB 250404A / EP250404a
- GRB 250404A / EP250404a: Mondy optical observations