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"23442 results found.
- GRB 250807A: SVOM/GRM observation
- GRB 250807A: AstroSat CZTI detection of bright long burst
- GRB 250807B: Swift-XRT refined Analysis
- EP250807a: EP-WXT detection of a fast X-ray transient
- EP 250807.979: GOTO optical upper limit
- EP250807a: COLIBRÍ optical upper limit
- GRB 250807A: SVOM/VT optical observation
- GRB 250807B: Enhanced Swift-XRT position
- GRB 250807A: Enhanced Swift-XRT position
- GRB 250807B: Swift detection of a burst with an optical counterpart.
- GRB 250805A: Kilonova-Catcher optical upper limits
- EP250806a:SVOM/VT refined analysis
- GRB 250805A: Swift/UVOT Upper Limits
- GRB 250806A: Swift/UVOT U-band detection
- EP250806a: Liverpool telescope optical upper limit
- GRB 250807A: Swift detection of a burst with an optical counterpart
- EP250802a: EP-FXT follow-up observation
- EP250806a: refined analysis of the EP-WXT and EP-FXT observations
- EP250806a: SVOM /VT optical candidate
- 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
- EP250806a: Einstein Probe detection of an X-ray transient
- GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250806A: SVOM/VT optical upper limit
- GRB 250806A: SVOM detection of a soft burst
- GRB 250805A: SVOM/VT optical counterpart
- 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
- GRB 250804B: SVOM/GRM observation of a short burst
- EP250802a: additional Liverpool Telescope upper limits
- EP250730a: SVOM/VT optical upper limit
- EP250802a: Liverpool Telescope optical upper limits
- EP250802a: GROWTH-India Telescope optical upper limit
- LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
- LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
- LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
- EP250711a: CrAO and Assy optical observations
- EP250730a: COLIBRÍ optical upper limit
- GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
- LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
- LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
- LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
- 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: 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
- LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
- GRB 250727A: SVOM detection of a burst
- Swift detection of the Soft Gamma Repeater PSR J1647-4552
- LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
- GRB 250725A: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
- 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: SVOM/VT optical candidate
- LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
- GRB 250725A: Enhanced Swift-XRT position
- GRB 250725A: Swift detection of a burst
- EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
- SVOM J195836+32283 is not a real source
- EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
- 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 250717B: SVOM/GRM observation
- The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
- EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
- GRB 250717B: COLIBRÍ optical upper limit
- GRB 250717B: Swift-XRT observations
- Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
- Swift Trigger 1334535: a possible GRB 250718A
- GRB 270713A: Kitab and AbAO Optical Observations
- GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250716A: Swift-XRT afterglow detection
- GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
- GRB 250714A: SVOM/GRM observation
- EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
- GRB 250713A: Mephisto optical upper limits
- 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