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"21791 results found.
- GRB 251222A / EP251222b: LCO optical observations
- GRB 251222A: 1.3m DFOT optical detection
- GRB251221A: 7DT optical upper limits
- EP251222a: GSP Optical Counterpart Detection
- GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
- EP251221a: Global MASTER-Net observations report
- GRB 251222A: PRIME near-infrared detection
- EP251221a: NOT optical upper limit
- GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- GRB 251222A: NOT optical observations
- IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
- GRB 251222A: Swift ToO observations
- SVOM GRB251222A: Global MASTER-Net observations report
- EP251220a: PRIME upper limit
- EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
- GRB 251221A: PRIME near-infrared observation
- EP251220a: NOT optical observations
- EP251220a: FTW optical and NIR observations
- GRB 251221A: UAFO and Mondy optical upper limit
- GRB 251221A: Swift/UVOT Upper Limits
- EP251220a: EP-FXT follow-up observation
- EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
- EP 251220a: GOTO optical counterpart detection
- EP 251220a: COLIBRÍ detection of the optical counterpart
- Swift GRB251221A: Global MASTER-Net observations report
- EP251220a: Global MASTER-Net observations report
- SVOM GRB251220.98: Global MASTER-Net observations report
- Fermi-LAT Gamma-ray Observations of IceCube-251218A
- GRB 251215A: Swift-XRT afterglow detection
- IceCube-251218A: COLIBRÍ optical upper limits
- SVOM GRB251219.11: Global MASTER-Net observations report
- IceCube Alert 251218.85: Global MASTER-Net observations report
- Fermi trigger No 787736968: Global MASTER-Net observations report
- Fermi GRB 251217A: Global MASTER-Net observations report
- GRB 251215A: Swift/UVOT Upper LImits
- Fermi GRB 251216A: Global MASTER-Net observations report
- GRB 251215A: COLIBRÍ optical upper limit
- GRB 251215A: Swift-XRT observations
- Fermi GRB 251215A: Global MASTER-Net observations report
- EP251214a: Optical upper limit with Kinder observations
- GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
- GRB 251214B: UAFO optical upper limit
- GRB 251214B: VLT/X-shooter observations
- GRB 251202A: radio detection with the VLA
- EP251214b: Global MASTER-Net observations report
- GRB 251214B: AbAO optical observations
- GRB 251214B: LCO detection of the optical counterpart
- GRB 251215A: Swift ToO observations
- EP251214b (EP trigger 01709250023): LCO optical limits
- GRB 251203B: AbAO optical observations
- GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251214B: Swift/UVOT Detection
- GRB 251214B: COLIBRÍ observations of the afterglow
- GRB 251214B: 1.3m DFOT optical detection
- EP251214a: Global MASTER-Net observations report
- GRB 251214B: Xinglong-2.16m optical observation
- GRB 251214B : MASTER optical afterglow detection
- Fermi trigger No 787396657: Global MASTER-Net observations report
- GRB 251214B: SVOM/C-GFT optical observations
- Swift GRB 251214B: Global MASTER-Net observations report
- Fermi GRB 251214A: Global MASTER-Net observations report
- EP251212a: Global MASTER-Net observations report
- EP251212a: KAIT optical upper limit
- IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
- Fermi-LAT Gamma-ray Observations of IceCube-251210A
- Fermi GRB 251211B: Global MASTER-Net observations report
- IceCube-251210A: DDOTI Optical Upper Limit
- SVOM GRB251211.12: Global MASTER-Net observations report
- GRB 251205A: 1.3m DFOT optical upper limit
- IceCube Alert 251210.46: Global MASTER-Net observations report
- GRB 251129A/EP251129a: AbAO and Mondy optical observations
- EP251130a: Mondy and AbAO optical observations
- Fermi GBM Sub-Threshold Detection of GRB 251205A
- Fermi GRB 251209A: Global MASTER-Net observations report
- Fermi GRB 251208C: Global MASTER-Net observations report
- GRB 251208B: Swift-XRT afterglow detection
- GRB 251208D: LAST optical upper limit
- GRB 251208D: LCO analysis of the XRT sources
- GRB 251208B: GROWTH-India Telescope optical upper limits
- GRB 251205A: J-band detection with WINTER
- GRB 251208D: Swift-XRT observations
- GRB 251129A: e-MERLIN C-band observations
- LAT GRB251208.43: Global MASTER-Net observations report
- GRB 251205A: Liverpool Telescope further optical follow-up observations
- SVOM GRB251208D: Global MASTER-Net observations report
- GRB 251208B: Swift ToO observations
- GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
- GRB 251205A : MITSuME Akeno optical afterglow candidate detection
- GRB 251205A: FTW optical and NIR observations
- EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
- GRB 251205A: Liverpool Telescope further optical follow-up observations
- SVOM GRB251206.86: Global MASTER-Net observations report
- GRB 251205A: ZTF and ATLAS optical afterglow detections
- GRB 251205A: GROWTH-India Telescope optical observations
- GRB 251205A: Swift/UVOT Detection
- GRB 251205A: Liverpool Telescope optical follow-up observations
- GRB 251203C: Swift/UVOT Upper Limit
- GRB 251205A: Zeiss-1000 Koshka observatory optical observations
- GRB 251205A: COLIBRÍ optical observations
- GRB 251205A: GOTO optical afterglow detection