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"19861 results found.
- GRB 260120B: Fermi GBM Observation
- EP260105a: GTC/HiPERCAM optical observations
- GRB 260120B: Swift/UVOT Detection
- GRB 260120B: COLIBRÍ optical upper limits
- GRB 260120B: Enhanced Swift-XRT position
- GRB 260120B: SVOM/C-GFT optical counterpart detection
- EP260116a: COLIBRÍ observations of a tentative optical rebrightening
- GRB 260120B: Swift detection of a burst
- EP260119A: Mondy I-Band Observations
- GRB 260114A: Swift/UVOT Upper Limits
- EP260119a: Liverpool Telescope optical follow-up observations
- GRB 251202A: further radio observations with the VLA
- EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
- EP260119a: KAIT optical observations
- EP260119a: SVOM/VT optical observation
- EP260119a: NOT optical observations
- EP260119a: SAO RAS optical observations
- EP260116a: COLIBRÍ detection of a fading optical source
- GRB 251208D: SVOM/ECLAIRs refined analysis
- GRB 251208D: SVOM/ECLAIRs refined analysis
- GRB 260117A: Swift-XRT afterglow detection
- EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
- EP260119a: LCO optical observations
- GRB 260117A: ZTSh optical upper limit
- EP260119a: COLIBRÍ optical counterpart candidate
- GRB 260110A: SVOM detection of a burst through offline search
- EP260119a: EP-WXT detection of a fast X-ray transient
- GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
- Fermi-LAT Gamma-ray Observations of IceCube-260115A
- Swift trigger on the HMXB 1A 1118-61
- GRB 260117A: SVOM/C-GFT upper limit
- GRB 260117A: SVOM detection of a long faint burst
- EP 260116a: COLIBRÍ optical upper limit
- Swift triggered on the HMXB 1A 1118-61
- FRB 20251229A: COLIBRÍ further inspection of the updated localization
- EP260116a: Liverpool Telescope upper limits
- EP260116A: 1.3m DFOT optical upper limit
- GRB 260114A: VLT/MUSE spectroscopic observations
- IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
- GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
- EP260116a: Xinglong optical upper limit
- EP260116a: Einstein Probe detection of an X-ray transient
- GRB 260114A: VLT/HAWK-I further near-infrared upper limits
- GRB 251222A: radio detection with the VLA
- GRB 260114A: VLT/HAWK-I near-infrared upper limits
- GRB 260114A: Swift-XRT refined Analysis
- GRB 260114A: 6 GHz VLA observations
- GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
- GRB 260114A : MITSuME Akeno optical upper limits
- GRB 260114A: COLIBRÍ optical upper limits
- GRB 260114A: TNG NIR upper limit
- GRB 260114A: NOT optical observations
- GRB 260114A: SVOM/GRM observation of a short burst
- GRB 260114A: Mondy optical observations
- GRB 260114A: GMG Optical Observation
- GRB 260114A: Swift detection of a short burst
- EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
- IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
- EP260110a: NOT and GTC Optical and Near-Infrared Observations
- EP260110a: TRT optical upper limits
- Swift Trigger 1439093: is probably not GRB 260113A
- GRB 260111A: COLIBRÍ optical afterglow candidate
- GRB 251230A: Mondy Optical Observations
- Swift trigger 1436759 is not an astrophysical event
- EP260110a: KAIT optical upper limit
- EP260110a: refined analysis of the EP-WXT and EP-FXT observations
- EP 260110a: COLIBRÍ optical observations
- EP260110a: SVOM/C-GFT upper limit
- EP260110a: Einstein Probe detection of an X-ray transient
- GRB 260109C: LCO optical upper limits
- GRB 260109C: Kilonova-Catcher optical upper limit
- Swift Trigger 1434591: possible GRB 260109C
- GRB 260102A: Swift-XRT afterglow detection
- GRB 260102A: AbAO optical observations
- EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
- Fermi GRB 260105A: Global MASTER-Net observations report
- GRB 260105A: SVOM/GRM observation
- GRB 260105B: SVOM/GRM observation
- FRB 20251229A: COLIBRÍ optical upper limits
- EP260105a: refined analysis of the EP-WXT and EP-FXT observations
- EP260105a: LCO Optical Upper limit
- EP260104a: Einstein Probe detection of a fast X-ray transient
- GRB 260101A: COLIBRÍ optical upper limits
- EP260105a: Einstein Probe detection of an X-ray transient
- GRB 260104A: COLIBRÍ optical upper limits
- GRB 260104C: Fermi GBM Final Real-time Localization
- GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
- GRB 260104A: Enhanced Swift-XRT position
- GRB 260101A: Swift/UVOT Detection
- GRB 260104A: Swift detection of a burst
- Fermi-LAT Gamma-ray Observations of IceCube-251225A
- GRB 260101A: COLIBRÍ optical observations
- GRB 260102A: LCO optical upper limits
- GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
- EP260101a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 260102A: SVOM detection of a burst
- GRB 260101A: NOT spectroscopic observations
- GRB 260101A: SVOM/GRM observation
- GRB 260101A: Enhanced Swift-XRT position
- EP260101a: Einstein Probe detection of an X-ray transient