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"12321 results found.
- GRB 250812A: Swift/UVOT Detection
- EP250812a: Liverpool Telescope upper limits
- IceCube Alert 250813.14: Global MASTER-Net observations report
- EP 250812a: GOTO optical upper limit
- EP250812a: Swift-XRT counterpart detection
- GRB 250812A: Swift-XRT afterglow detection
- IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
- Fermi-LAT Gamma-ray Observations of IceCube-250804A
- GRB 250809A: Swift/UVOT Detection
- EP250807a: EP-FXT follow-up observation upper limit
- GRB 250809A: LCOGT Optical Upper Limits
- EP250807a: Global MASTER-Net observations report
- Fermi GRB 250808A: Global MASTER-Net observations report
- GRB 250809A: Swift detection of a gamma ray burst
- GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250808A: Swift-XRT candidate counterpart detection
- Konus-Wind detection of GRB 250807A
- IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250807A: Swift/UVOT Detection
- EP250807a: NTT z-band optical upper limit
- GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
- Swift GRB250807.45: Global MASTER-Net observations report
- GRB 250806A: NOT z-band upper limit and host galaxy candidate
- EP250807a: EP-WXT detection of a fast X-ray transient
- EP 250807.979: GOTO optical upper limit
- EP250807a: COLIBRÍ optical upper limit
- EP250806a: Upper limit from Fermi-GBM Observations
- Swift GRB250807.65: Global MASTER-Net observations report
- IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
- GRB 250805A: Kilonova-Catcher optical upper limits
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- EP250806a: Liverpool telescope optical upper limit
- IceCube Alert 250804.84: Global MASTER-Net observations report
- EP#01709198415/EP250806a: Swift-XRT observations
- EP250806a: Global MASTER-Net observations report
- GRB 250806A: J-band upper limit from WINTER
- GRB 250806A: KAIT optical upper limit
- GRB 250806A: SVOM/VT refined analysis
- EP250806a: COLIBRÍ optical upper limit
- GRB 250806A: Kilonova-Catcher optical upper limits
- GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250806A: SVOM/VT optical upper limit
- GRB 250804B: Swift-XRT observations
- GRB 250805A: TRT optical upper limits
- Swift GRB250805.26: Global MASTER-Net observations report
- Fermi trigger No 776041355: Global MASTER-Net observations report
- EP250802a: additional Liverpool Telescope upper limits
- EP250730a: SVOM/VT optical upper limit
- EP250802a: Liverpool Telescope optical upper limits
- EP250802a: Global MASTER-Net observations report
- EP250802a: GROWTH-India Telescope optical upper limit
- GRB 250702B: SMA observations
- EP250730a: Global MASTER-Net observations report
- EP250730a: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
- LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- GRB 250727A: EP-FXT follow-up observation
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
- LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
- GRB 250728A: Swift-XRT observations
- GRB 250728A: COLIBRÍ optical upper limit
- Fermi trigger No 775387550: Global MASTER-Net observations report
- GRB 250727A: AST3-2 Upper limit
- GRB250727A: SVOM/VT optical upper limit
- GRB 250727A: Swift-XRT observations
- GRB 250725A: Swift/UVOT Upper Limits
- GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
- GRB 250725A: Swift detection of a burst
- Swift GRB 250725A: Global MASTER-Net OT detection
- Fermi GRB 250725A: Global MASTER-Net observations report
- Swift GRB 250725A: Global MASTER-Net observations report
- SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
- SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
- SVOM J195836+32283/sb25072103: NIR observations with WINTER
- GRB 250721A: Swift-XRT observations
- GRB 250721A: MAXI/GSC detection
- Fermi trigger No 774730635: Global MASTER-Net observations report
- EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
- GRB 250717B: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
- GRB 250717B: Swift-XRT observations
- Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
- Swift GRB250718.01: Global MASTER-Net observations report
- GRB 250716A: Swift-XRT afterglow detection
- Fermi GRB 250716A: Global MASTER-Net observations report
- Fermi GRB 250715A: Global MASTER-Net observations report
- GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
- GRB 250713A: Mephisto optical upper limits
- Fermi GRB 250714A: Global MASTER-Net observations report
- GRB 250713A: SVOM/VT optical upper limit
- GRB 250713A: NOT optical upper limits
- GRB 250713A: OHP/T193 upper limit
- GRB 250713A: SVOM/C-GFT upper limit
- GRB 250706B/C: 7DT Follow-up Observations
- GRB 250713A: Swift-XRT observations
- GRB 250713A: JinShan optical upper limits