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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
23918 results found.
- LIGO/Virgo/KAGRA S250202cu: Identification of a GW compact binary merger candidate
- GRB 250129A: SVOM/C-GFT optical observations
- GRB 250202B: AstroSat CZTI detection of a bright long GRB
- Swift GRB250129A: MASTER 4 days observations report
- GRB 250129A: 1.3m DFOT Optical observations
- GRB 250201A: BALROG localization (Fermi Trigger 760096791 / GRB 250201417)
- GRB 250201A: Fermi GBM Final Real-time Localization
- LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
- GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
- EP250108A / SN 2025kg: Upper limits from a neutrino search with IceCube
- GRB 250129A: SAO RAS optical observations
- GRB 250129A: COLIBRÍ Continuing Detection of the Afterglow
- GRB 250129A: COLIBRÍ Optical Observations
- GRB 250129A: iTelescope optical observation
- GRB 250129a: Liverpool Telescope optical follow-up
- GRB 250129A: TNG NIR afterglow detection
- GRB 250129A: AKO Optical Afterglow Detection
- 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: Swift-XRT refined Analysis
- GRB 250128B: Gemini-North optical extended source detection
- GRB 250128B: TNG optical upper limit
- GRB 250129A: Swift/UVOT Detection
- GRB 250128B: VLT/HAWKI near-infrared observations
- GRB 250127A: CrAO and Terskol optical upper limits
- GRB 250129A: Enhanced Swift-XRT position
- GRB 250128B: NOT optical upper limit
- 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 250128B: OHP/T193 optical upper limit
- GRB 250129A: LCO optical observations
- GRB 250128B: Enhanced Swift-XRT position
- GRB 250129A: Swift detection of a burst with an optical counterpart
- Swift GRB250129A: Global MASTER-Net OT detection
- GRB 250128B: Swift-XRT refined Analysis
- GRB 250128B: GOTO optical upper limit
- EP250125a: Upper limits from Swift/BAT-GUANO
- GRB 250128B: LCO optical observations
- GRB 250128B: Swift detection of a short burst
- GRB 250127A: Swift-XRT observations
- GRB 250127B: DDOTI Upper Limit on the Afterglow
- Fermi-LAT Gamma-ray Observations of IceCube-250102A
- Fermi GRB 250128A: Global MASTER-Net observations report
- GRB 250117A: Fermi GBM Observation
- Fermi-LAT Gamma-ray Observations of IceCube-250101A
- IPN triangulation of GRB 250119C
- GRB 250127A: LCO optical upper limit
- GRB 241223A: cubesat Avion detection
- EP250125A: Non-detection from Fermi-GBM Observations
- GRB 250126A: MAXI/GSC detection
- GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
- EP250125a: Optical upper limit with Kinder observations
- EP250125a: REM optical counterpart detection
- GRB 250119C: Fermi GBM Observation
- EP250125a: Swift/XRT detection of a fading counterpart
- EP250125a: a new X-ray transient detected by Einstein Probe
- EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
- GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
- EP250108a: AbAO, CMO and Terskol optical upper limits
- GRB 250121A: Fermi GBM Observation
- IPN triangulation of GRB 250118B
- IPN triangulation of GRB 250119B
- GRB 250114A: Swift-BAT refined analysis
- LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
- GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
- Fermi-LAT Gamma-ray Observations of IceCube-241224A
- GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250119B: Fermi GBM Observation
- EP250108a/AT2025kg: 1.3m DFOT Optical observations
- IPN triangulation of GRB 250117A (short)
- LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
- EP 250108A: Late-time optical observation by LCO
- LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
- LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
- LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
- LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
- GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
- LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
- GRB 250117A: GECAM observation of a short burst
- LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
- GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
- LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
- LIGO/Virgo/KAGRA S250118t: Updated Sky localization
- LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
- EP250108a / AT2025kg: GMG Optical Observations
- LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
- GRB 241217A / EP241217B: radio detection with the VLA
- GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
- GRB 250114B: Swift-XRT afterglow detection
- EP250108a: MeerKAT radio upper limit
- LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
- GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.