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"
17213 results found.
- GRB 250221A: GRANDMA/TAROT Detection
- GRB 250221A: 1.6m Mephisto optical detection
- GRB 250221A: AKO Optical Upper Limit
- GRB 250221A: Swift/UVOT Detection
- EP250220a: Liverpool Telescope upper limits
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- GRB 250221A: REM optical/NIR afterglow detection
- GRB 250221A: Enhanced Swift-XRT position
- EP250220a: 1.6m Mephisto observations
- EP250220a: Liverpool Telescope optical upper limits
- EP250220a: Optical upper limit with Kinder observations
- SVOM trigger sb25022102 is not an astrophysical event
- SVOM/sb25022102: SVOM detection of an X-ray transient
- GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
- GRB 250221A: Swift detection of a burst with an optical counterpart
- EP250220a: Xinglong optical upper limit
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: OHP/T193 optical upper limit
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- LIGO/Virgo/KAGRA S250206dm: Upper limits from MSU cubesats observations
- GRB 250219A: Swift ToO observations
- GRB 250219A: SVOM detection of a burst
- SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
- GRB 250217C: Swift-XRT observations
- SVOM/sb25021804: QSO variability in Liverpool Telescope observations
- GRB 250217C: COLIBRÍ/DDRAGO Upper Limits on the Optical Counterpart
- GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
- GRB 250217C: SVOM/GRM observation
- GRB 250217C: Tiled Swift observations
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- LIGO/Virgo/KAGRA S250206dm: AZT-33IK Target Optical Observations
- GRANDMA/OPD observations of GRB250215A
- GRB 250215A / EP250215a: LCO detection of the afterglow
- GRB 250215A: Swift/UVOT Upper Limits
- GRB 250215A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A/EP250215a: 1.6m Mephisto optical observation report
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: SVOM/GRM observation
- EP250215a / GRB 250215A: AstroSat CZTI detection
- EP250215a / GRB 250215A (potentially): NOT likely optical counterpart
- EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
- EP250207b: Xinglong optical upper limit
- GRB 250213A: Swift ToO observations
- EP250212a: Xinglong optical upper limit
- LIGO/Virgo/KAGRA S250206dm: DECam GW-MMADS candidates
- GRB 250213A: SVOM detection of a burst
- GRB 250205A: VIRT Optical Upper Limit
- GRB 250205A: Leavitt Observatory optical upper limit
- EP250207B: Chandra localization of the X-ray counterpart
- EP250212a: Liverpool Telescope optical upper limits
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- EP250207B: GTC z-band Observations
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
- GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- EP250207b: NOT optical counterpart candidate
- LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
- GRB 250211A: Swift ToO observations
- LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
- GRB 250206A: Fermi GBM Observation
- GRB 250205A / EP250205A: radio detection with the VLA
- EP250207b: Tentative z-band brightening source
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- GRB 250210A: SVOM/GRM observation of a long burst
- EP250207b: Liverpool Telescope possible optical counterpart
- LIGO/Virgo/KAGRA S250211aa: Identification of a GW compact binary merger candidate
- GRB 250207A: Skynet optical afterglow observations
- GRB 241128A: VIRT Optical Upper Limit
- EP250207b: Gemini GMOS-N z-band observations
- EP250207b: a new X-ray transient detected by Einstein Probe
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
- LIGO/Virgo/KAGRA S250206dm: Optical observations of candidate AT 2025bbo with Kinder
- Fermi-LAT Gamma-ray Observations of IceCube-250207A
- GRB 250207A: 1.3m DFOT Optical observations
- LIGO/Virgo/KAGRA S250206dm: WFST follow-up observations
- LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
- GRB 250129A: GRANDMA Continued Afterglow Detection
- LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
- GRB 250205A: 1.3m DFOT optical upper limit
- GRB 250206A: Tiled Swift observations
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
- GRB 250207B: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
- GRB 250208A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
- EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
- GRB 250207A: Enhanced Swift-XRT position
- CHIME/FRB source FRB 20250206A detected less than 1 minute after LIGO-Virgo-Kagra (LVK) S250206dm, however the probability of spatial coincidence is order 0.1%
- GRB 250129A: ABObservatory SLOAN r’ afterglow detection
- GRB 250207A: REM IR afterglow detection
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
- GRB 250207B: Tiled Swift observations
- IGO/Virgo/KAGRA S250206dm: Virtual Telescope Project upper limit for the Neutrino IceCube Candidate
- GRB 250207A: REM optical afterglow detection
- GRB 250207A: Swift/UVOT Detection
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limit for the Neutrino IceCube Candidate
- LIGO/Virgo/KAGRA S250206dm: GOTO observations of optical candidates AT 2025azn and AT 2025azm