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"20960 results found.
- EP250212a: Global MASTER-Net observations report
- GRB 250205A: Leavitt Observatory optical upper limit
- EP250207B: Chandra localization of the X-ray counterpart
- LIGO/Virgo/KAGRA S250206dm: FTW observations of counterpart candidates AT2025bbo and AT2025bcx, and of NED galaxies
- EP250207b: VLA radio upper limits
- GRB250101A: Radio upper limits from GMRT observations
- EP trigger 10202399251 (possibly EP250212a): NOT J-band upper limit
- EP250207B: GTC z-band Observations
- Fermi GRB 250212A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: NEWFIRM NIR Follow-up of AT2025ber
- GRB 250205A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- Fermi trigger No 760945500: Global MASTER-Net observations report
- EP250207b: NOT optical counterpart candidate
- LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
- GRB 250211A: Swift ToO observations
- Integral GRB250211.89: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: AT 2025bbo observations with WFST
- GRB 250205A / EP250205A: radio detection with the VLA
- IceCube-250207A: One candidate from the Zwicky Transient Facility
- EP250207b: Tentative z-band brightening source
- LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
- LIGO/Virgo/KAGRA S250206dm: Kinder confirmation of a possible artefact in AT 2025bbo
- EP250207b: Liverpool Telescope possible optical counterpart
- EP250207b: Global MASTER-Net observations report
- Gemini-South spectroscopic redshift of EP250207b host galaxy candidate (z=0.082)
- GRB 250207A: Skynet optical afterglow observations
- LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
- LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
- EP250207b: Gemini GMOS-N z-band observations
- EP250207A: Upper limits from Fermi-GBM Observations
- GRB 250210A: INTEGRAL SPI-ACS detection
- EP250207b: a new X-ray transient detected by Einstein Probe
- Fermi GRB 250210A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: Upper limits from GECAM Observations
- LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
- IceCube Alert 250207.09: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: Observations from WINTER
- 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
- GRB 250129A: GRANDMA Continued Afterglow Detection
- 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
- EP-WXT trigger 01709131361: correction to GCN 39214
- EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
- 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
- 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