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"
19128 results found.
- GRB 250807A: Swift-XRT refined Analysis
- GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
- GRB 250806A: SVOM/MXT refined analysis
- GRB 250806A: SVOM/ECLAIRs refined analysis
- GRB 250807A: SVOM/GRM observation
- Swift GRB250807.45: Global MASTER-Net observations report
- GRB 250807A: AstroSat CZTI detection of bright long burst
- GRB 250807B: Swift-XRT refined Analysis
- GRB 250807B: NTT optical observations
- GRB 250807A: SVOM/VT optical observation
- GRB 250807B: Enhanced Swift-XRT position
- Swift GRB250807.65: Global MASTER-Net observations report
- GRB 250807A: Enhanced Swift-XRT position
- GRB 250807B: Swift detection of a burst with an optical counterpart.
- GRB 250805A: Kilonova-Catcher optical upper limits
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- GRB 250807A: Swift detection of a burst with an optical counterpart
- GRB 250806A: EP-FXT observation
- EP#01709198415/EP250806a: Swift-XRT observations
- GRB 250805A: Swift-BAT refined analysis
- GRB 250806A: KAIT optical upper limit
- GRB 250806A: SVOM/VT refined analysis
- GRB 250806A: Swift-XRT counterpart detection
- GRB 250805A: SVOM/VT optical counterpart
- GRB 250805A: ESO/VLT observations
- GRB 250805A: Swift-XRT refined Analysis
- GRB 250804B: Swift-XRT observations
- GRB 250805A: Enhanced Swift-XRT position
- GRB 250805A: TRT optical upper limits
- GRB 250805A: Swift-XRT observations
- GRB 250805A: Swift detection of a burst
- Swift GRB250805.26: Global MASTER-Net observations report
- GRB 250804B: Tiled Swift observations
- LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
- LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- 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 250725A: AstroSat CZTI detection
- GRB 250727A: EP-FXT follow-up observation
- GRB 250725A: PRIME near-infrared observations
- 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
- GRB 250728A: Fermi GBM Observation
- LIGO/Virgo/KAGRA S250727dc: Swift-UVOT detection of a new source, AT 2025smm
- GRB 250728A: Swift ToO observations
- GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
- GRB 250727A: EP-FXT counterpart detection
- GRB250727A: SVOM/VT optical upper limit
- GRB 250727A: Swift-XRT observations
- Swift detection of the Soft Gamma Repeater PSR J1647-4552
- GRB 250725A: Swift-XRT refined Analysis
- GRB 250725A: Fermi GBM Observation
- GRB 250725A: Swift-BAT refined analysis
- Konus-Wind detection of GRB 250725A
- GRB 250725A: SVOM/GRM observation
- GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
- GRB 250725A: Swift/UVOT Upper Limits
- GRB 250725A: Fermi-LAT detection
- GRB 250725A: BOOTES-7 early optical detection
- GRB 250725A: SVOM/VT optical candidate
- GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
- GRB 250725A: Enhanced Swift-XRT position
- GRB 250725A: Swift detection of a burst
- Swift GRB 250725A: Global MASTER-Net OT detection
- Swift GRB 250725A: Global MASTER-Net observations report
- SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
- Swift-BAT trigger 1334535 is not a GRB
- GRB 250721A: Swift-XRT observations
- GRB 250717B: SVOM/GRM observation
- GRB 250721A: Tiled Swift observations
- 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 Trigger 1334535: a possible GRB 250718A
- Swift GRB250718.01: Global MASTER-Net observations report
- GRB 250717B: Swift ToO observations
- GRB 270713A: Kitab and AbAO Optical Observations
- GRB 250717B: Fermi GBM Observation
- GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250716A: Swift ToO observations
- GRB 250713A: SVOM/C-GFT upper limit
- GRB 250713A: Swift-XRT observations
- GRB 250706A: Swift-BAT refined analysis
- GRB 250702F: Swift-BAT refined analysis
- GRB 250628A: Swift-BAT refined analysis
- LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
- LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
- GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
- GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
- GRB 250706B/C: Fermi-LAT detection
- GRB 250706B: Swift/UVOT Detection