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.
Lucene Examples (click to copy):
subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
19138 results found.
- LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
- 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
- GRB 250206A: Swift-XRT observations
- LIGO/Virgo/KAGRA S250206dm: FRB 20250206A BOOTES-5 and 2.2m CAHA optical upper limits
- LIGO/Virgo/KAGRA S250206dm: further Pan-STARRS observations and one candidate AT2025bbo
- LIGO/Virgo/KAGRA S250207bg: Updated NED Galaxies in the Localization Volume
- 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: (Update-7) NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Observations
- GRB 250207B: Swift-XRT observations
- IceCube-250203A: No transient candidates from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S250206dm: Spectroscopic Classification of AT2025bay and AT2025baz with Keck I/LRIS
- LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the DDOTI optical candidates
- LIGO/Virgo/KAGRA S250206dm: MMT galaxy targeted observations
- LIGO/Virgo/KAGRA S250206dm: FRB 20250206A & "Time Machine" Effect.
- EP-WXT trigger 01709131361: correction to GCN 39214
- EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
- 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%
- LIGO/Virgo/KAGRA S250206dm: GOTO counterpart search update - AT2025bar
- EP-WXT trigger 01709131361 / LIGO/Virgo/KAGRA S250206dm: FTW optical and NIR observations
- GRB 250129A: ABObservatory SLOAN r’ afterglow detection
- GRB 250207A: REM IR afterglow detection
- LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
- LIGO/Virgo/KAGRA S250206dm: Pan-STARRS survey of the skymap for optical transients
- GRB 250207A: FRAM-Auger optical detection
- LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
- GRB 250207B: Tiled Swift observations
- LIGO/Virgo/KAGRA S250207bg: NED Galaxies in the Localization Volume
- GRB 250207A: REM optical afterglow detection
- LIGO/Virgo/KAGRA S250206dm:GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- 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
- LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
- LIGO/Virgo/KAGRA S250206dm: Pan-STARRS observations of AT2025azm and AT2025azn
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of the AT 2025azn Optical Candidate
- GRB 250129A: Continued AbAO and Mondy optical observations
- LIGO/Virgo/KAGRA S250206dm: SAGUARO Detection of Two Potential Optical Counterparts
- GRB 250207A: COLIBRÍ/DDRAGO Optical Afterglow Detection
- LIGO/Virgo/KAGRA S250206dm: Updated-6 NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: Upper limits from Fermi-GBM Observations
- Fermi-LAT Gamma-ray Observations of IceCube-250203A
- LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
- LIGO/Virgo/KAGRA S250206dm: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250206dm: Two counterpart neutrino candidates from IceCube neutrino searches
- LIGO/Virgo/KAGRA S250206dm: NED Galaxies in the Localization Volume
- GRB 250205A: REM NIR upper limit
- EP250205a/GRB 250205A: FTW optical and NIR observations of the counterpart
- GRB 250205A: Swift/UVOT Upper Limits
- GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
- GRB 250205A: Swift/XRT detection
- GRB 250205A: GOTO optical upper limits
- GRB 250205A: OHP/T193 optical counterpart candidate
- GRB 250205A: Liverpool Telescope optical counterpart candidate detection
- LIGO/Virgo/KAGRA S250205bk: NED Galaxies in the Localization Volume
- EP 250108A: Upper limits from Fermi-GBM Observations
- GRB 250129A: LCO late afterglow detection
- GRB 250129A: AbAO AS-32 and Mondy AZT-33IK optical observations
- GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
- GRB 250129a: Liverpool Telescope optical follow-up
- GRB 240129A: further SAO RAS optical observations
- GRB 250129A: 7DT Detection and Medium-band SED of Afterglow
- GRB 250129A: SVOM/C-GFT optical observations
- Swift GRB250129A: MASTER 4 days observations report
- GRB 250201A: INTEGRAL SPI/ACS detection
- GRB 250129A: 1.3m DFOT Optical observations
- GRB 250129A: Liverpool Telescope observations suggest continued engine activity
- LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
- GRB 250129A: Skynet Continued Optical Observations
- GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
- GRB 250129A: SAO RAS optical observations
- GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
- GRB 250129A: optical photometry from Konkoly
- GRB 250129A: COLIBRÍ Optical Observations
- GRB 250128B: VLA possible radio detection
- GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
- GRB 250129A: NOT optical observations of continuining activity
- GRB 250129a: Liverpool Telescope optical follow-up
- GRB 250129A: GRANDMA/TAROT optical afterglow detection
- GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
- GRB 250128B: VLA radio upper limit
- Ep250125A: 1.3m DFOT optical upper limit
- GRB 250129A: Skynet optical observations
- GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
- GRB 250128B: Gemini-North optical extended source detection
- The EP-WXT trigger 01709131085: KAIT confirmation of the stellar flare
- GRB 250129A: Swift/UVOT Detection
- GRB 250128B: VLT/HAWKI near-infrared observations
- GRB 250127A: CrAO and Terskol optical upper limits
- GRB 250128B: VLT/FORS2 optical observations
- GRB 250129A: REM optical/NIR afterglow detection
- GRB 250129A: OHP/T193 optical and spectroscopy observations
- GRB 250129A: Early afterglow detection by LCO.
- GRB 250129A: LCO optical observations