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"
4571 results found.
- EP250512a: Global MASTER-Net observations report
- Fermi GRB 250510C: Global MASTER-Net observations report
- GRB 250510C: Fermi GBM Final Real-time Localization
- IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
- GRB 250509A: Swift-XRT refined Analysis
- EP250508a: Liverpool Telescope optical upper limits
- GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
- EP250508a: Global MASTER-Net observations report
- GRB 250504A: Swift-XRT refined Analysis
- Fermi GRB 250502B: Global MASTER-Net observations report
- GRB 250430A: SVOM/VT optical observations
- GRB 250424A: CALET Gamma-Ray Burst Monitor detection
- Fermi trigger No 767623859: Global MASTER-Net observations report
- EP250428b: SAO RAS optical upper limit
- GRB 250424A: LCO optical observation
- EP250427a: TRT optical counterpart detection
- GRB 250424A: WINTER J-band detection
- GRB 250424A: EIRSAT-1 GMOD Detection
- GRB 250424A: SVOM/VT optical observation
- GRB 250424A: Swift-XRT refined Analysis
- GRB 250424A: AstroSat CZTI detection of a bright long burst
- GRB 250424A: BlackGEM optical afterglow detection
- GRB 250424A: DDOTI Afterglow Detection
- GRB 250424A: REM optical/NIR afterglow detection
- Swift GRB250424A: Global MASTER-Net observations report
- Swift GRB250424A: Global MASTER-Net OT detection
- SVOM/sb25042207: BOOTES-2 early optical upper limit
- EP250421a: Swift/XRT counterpart detection
- Fermi GRB 250421A: Global MASTER-Net observations report
- IceCube Alert 250421.71: Global MASTER-Net observations report
- EP250421a: JinShan likely optical counterpart
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
- IceCube-250416A: DDOTI Optical Observations
- EP250404a: Nanshan 0.43m Telescope optical observatios
- Fermi trigger No 766148493: Global MASTER-Net observations report
- Fermi trigger No 766173972: Global MASTER-Net observations report
- Fermi GRB 250411A: Global MASTER-Net observations report
- IPN triangulation of GRB 250407A
- Fermi GRB 250407A: Global MASTER-Net observations report
- IceCube 250406.951: DDOTI Optical Observations
- IceCube Alert 250406.95: Global MASTER-Net observations report
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
- GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- GRB 250403A: Montarrenti Observatory optical detection
- EP250404a: Global MASTER-Net observations report
- EP250404a: Nanshan/HMT optical counterpart detection
- GRB 250403A: Swift/UVOT Detection
- EP250402a: Optical upper limit with Kinder observations
- GRB 250403A: Swift-XRT observations
- GRB 250403A: GOTO optical counterpart follow-up observations
- GRB 250403A: GMG Optical Observation
- GRB 250331C: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- Fermi GRB 250331E: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250331B: Swift detection of a burst
- GRB 250331A: MAXI/GSC detection
- GRB 250330A: Swift-XRT afterglow detection
- IceCube Alert 250330.35: Global MASTER-Net observations report
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327A: Swift-XRT refined Analysis
- GRB 250327B: GOTO optical counterpart detection
- FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
- EP250324A: COLIBRÍ/DDRAGO Optical Observations
- GRB 250322A: Swift-XRT refined Analysis
- GRB 250322A: AstroSat CZTI detection of a short burst
- FRB 250316A: DDOTI Continued Optical Observations
- EP250321a: Liverpool Telescope optical follow-up
- GRB 250312A: GECAM-A detection
- GRB 250321A: Swift-BAT refined analysis
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- Fermi GRB 250316A: Global MASTER-Net observations report
- GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
- Fermi GRB 250313A: Global MASTER-Net observations report
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250312A: Swift detection of a burst
- GRB 230509B: 1.3m DFOT Optical observations
- IPN triangulation of GRB 250308A (short)
- IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
- GRB 250309B: Swift-XRT refined Analysis
- IceCube Alert 250309.32: Global MASTER-Net observations report
- Fermi GRB 250307A: Global MASTER-Net observations report
- Fermi trigger No 762963055: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
- Konus-Wind detection of GRB 250222A
- IPN triangulation of GRB 250222A
- EP250302a: Global MASTER-Net observations report
- Fermi GRB 250302A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
- EP250228a: Optical observations with Kinder and Swift/UVOT
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250223a: J band upper limit by SYSU 80cm telescope