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').
19109 results found.
- GRB 250403A: Montarrenti Observatory optical detection
- GRB 250403A: KAIT optical observations
- EP250404a: AKO Optical Afterglow Detection
- EP250404a: LAST detection of optical counterpart
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250327B: VIRT Optical Upper Limit
- EP250404a: Mephisto multi-band optical detection
- EP250321A: J band upper limit by SYSU 80cm telescope
- EP250404a: Nanshan/HMT optical counterpart detection
- EP250404a: Einstein Probe detection of an X-ray transient
- GRB 250403A: Swift/UVOT Detection
- GRB 250402A: Swift/UVOT Upper Limits
- EP250402a: Optical upper limit with Kinder observations
- GRB 250403A: REM NIR afterglow detection
- GRB 250403A: LCO optical counterpart detection
- IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
- GRB 250403A: JinShan optical observations
- GRB 250403A: Optical counterpart detection by LCO.
- GRB 250402A: NUTTelA-TAO Early Optical Limits
- GRB 250403A: GMG Optical Observation
- GRB 250403A: 1.6m Mephisto multi-band optical detection
- GRB 250403A: SVOM/C-GFT optical observations
- GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- GRB 250402A: REM optical/NIR upper limits
- GRB 250402A: LCO optical counterpart detection
- EP250402a: Einstein Probe detection of a fast X-ray transient
- GRB 250402A: SVOM/VT optical counterpart
- GRB 250402A: SVOM detection of a burst
- GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250329B: Swift/UVOT Upper Limit
- GRB 250329A: Swift/UVOT Upper Limit
- GRB 250327B: Swift/UVOT Detection
- GRB 250327A: Swift/UVOT Upper Limits
- GRB 250331E: SVOM/GRM observation
- GRB 250327B: Kilonova-Catcher Observations
- GRB250331D: AbAO optical observations
- GRB 250331C: Swift/UVOT Upper Limits
- GRB 250331B: Swift/UVOT Upper Limits
- GRB 250328A: AbAO AS-32 Optical Observations
- GRB 250219A: NOT candidate host galaxy detection
- GRB 250322B: GRBAlpha detection
- GRB 250330B: SVOM/GRM observation of a short burst
- GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
- GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
- Konus-Wind detection of GRB 250327B
- GRB 250331C: Enhanced Swift-XRT position
- GRB 250331B: Enhanced Swift-XRT position
- GRB 250330A: VLT/FORS2 Afterglow Detection
- GRB20250327B: 45th Parallel Observatory upper limit
- GRB 250328A: Swift/UVOT Detection
- GRB 250328A: Swift-XRT refined Analysis
- Fermi-LAT gamma-ray observations of IceCube-250330A
- GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
- GRB 250330A: Swift/UVOT Upper Limits
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250328A: 1.6m Mephisto optical observations
- GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
- GRB 250330A: VLT/FORS2 Optical Observations
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- GRB 250329B: SVOM/C-GFT optical upper limit
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- GRB250329A: REM optical afterglow detection
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250328A: SVOM/VT optical observation
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250328A: SVOM/C-GFT optical upper limit
- GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
- GRB 250329A: SVOM/VT optical counterpart confirmation
- GRB 250329A: SVOM detection of a burst
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: J-band observations with WINTER
- GRB 250327B: LCO optical counterpart detection
- EP250302a: SPI-ACS/INTEGRAL Upper Limit
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327b: Liverpool Telescope optical observations
- GRB 250322A: GRANDMA/TNOT optical upper limits
- GRB 250327A: SVOM/VT upper limits on the XRT position
- LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250327B: Las Cumbres optical counterpart detection
- GRB 250327B: 1.6m Mephisto optical observations
- GRB 250327B: SVOM/VT optically bright counterpart
- GRB 250327B: SAO RAS optical candidate
- GRB 250327B: SVOM detection of a burst
- GRB 250327A: J-band observations with WINTER
- GRB 250327A: SVOM/VT optical candidate
- FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- Konus-Wind detection of GRB 250322A (short)
- IPN triangulation of GRB 250322B
- LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
- EP250321a: Mondy AZT-33IK Continued Optical Observations
- Swift follow-up observations of FRB250316A and EP J120944.2+585060