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"28076 results found.
- EP250508a: follow-up observation with EP-FXT
- EP250508a: KAIT optical upper limit
- GRB 250507A: KAIT optical upper limit
- GRB 250506A: GECAM detection
- GRB 250506A: Swift-XRT afterglow detection
- GRB 250506A: SVOM/VT optical upper limit
- EP250508a: Einstein Probe detection of an X-ray transient
- GRB 250507A: Swift-XRT refined Analysis
- GRB 250506A: Swift/UVOT Upper Limits
- GRB 250427B : SVOM detection of a burst through offline search
- GRB 250430A / EP250430a: AstroSat CZTI detection
- EP#01709175213/IGR J19566+0326: Swift-XRT detection
- GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
- GRB 250506A: Swift-XRT observations
- EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
- GRB 250507A: SVOM detection of a long burst
- GRB 250504A: EIRSAT-1 GMOD Detection
- GRB 250506A: Swift ToO observations
- IceCube-250506A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
- GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
- GRB 250506A: Swift XRT observations and possible counterpart detection
- GRB 250506A: TRT optical observations
- GRB 250506A: SVOM detection of a burst
- GRB 250506A: Fermi GBM Final Real-time Localization
- GRB 250504A: Swift-XRT refined Analysis
- GRB 250504A: VLT/X-shooter upper limits
- GRB 250504A: SVOM/VT upper limit
- GRB 250504A: REM optical/NIR observations
- GRB 250502A: REM optical/NIR observations
- GRB 250505A: Fermi GBM Final Real-time Localization
- GRB 250504A: MeerLICHT optical afterglow detection
- GRB 250504A: Enhanced Swift-XRT position
- GRB 250504A: Swift detection of a burst
- GRB 250504A: Fermi GBM Final Real-time Localization
- GRB 250502A: Mondy and Tien-Shan Optical Observations
- GRB 250502A: KAIT optical observations
- GRB 250502A: Montarrenti Observatory optical detection
- GRB 250502A: Swift-XRT afterglow detection
- GRB 250502a: Liverpool Telescope optical follow-up
- GRB 250502B: AstroSat CZTI detection
- GRB 250502A: AKO Optical Afterglow Detection
- GRB 250502A: LCO optical counterpart detection
- GRB 250502A: Swift ToO observations
- GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
- GRB 250502C: Fermi GBM Final Localization
- GRB 250407A: VZLUSAT-2 detection
- GRB 250430A: Swift-XRT refined Analysis
- GRB 250502A: Early optical counterpart detection by LCO.
- GRB 250430A: Swift/UVOT Detection
- GRB 250502A: TRT optical afterglow confirmation
- GRB 250430A: Enhanced Swift-XRT position
- GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
- GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250502B: Fermi GBM Final Real-time Localization
- GRB 250502A: SVOM detection of a burst
- GRB 250430A: SVOM/VT optical observations
- GRB 250430A: KAIT optical observations
- EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
- GRB 250430A: NUTTelA-TAO Early Measurements
- EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
- GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
- EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
- GRB 250424A: CALET Gamma-Ray Burst Monitor detection
- GRB 250430A: AKO Optical Afterglow Detection
- EP 250427A: Optical counterpart detection by LCO.
- GRB 250430A: Swift detection of a burst with optical counterpart
- EP250427a / GRB 250427A: OHP/T193 continued photometric observations
- SVOM/sb25043004: SVOM detection of a X-ray transient
- EP250428b: refined analysis of the EP-FXT follow-up observation
- IceCube-250429A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250427A: Swift/UVOT Detection
- EP250428b: Einstein Probe detection of a fast X-ray transient
- EP250427a / GRB 250427A: OHP/T193 photometric observations
- EP250427a: EP-FXT follow-up observations
- EP250427a: Lesedi optical counterpart detection
- GRB250427A/EP250427a GIT optical afterglow detection:
- EP250427a: LT optical counterpart detection
- GRB 250427A: Swift-XRT refined Analysis
- EP250427a / GRB 250427A: LCO optical counterpart detection
- EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
- EP250427A/GRB250427A: Keck/LRIS redshift
- EP250427a: REM optical/NIR afterglow detection
- GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
- EP250427A: COLIBRÍ Optical Detection
- EP250427a: TRT optical counterpart detection
- EP 250427a: BOOTES-7 optical afterglow candidate
- EP250427a: Einstein Probe detection of a fast X-ray transient
- IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
- GRB 250424A: PRIME near-infrared detection
- GRB 250424A: WINTER J-band detection
- GRB 250424A: EIRSAT-1 GMOD Detection
- GRB 250424A: Swift/UVOT Detection
- Konus-Wind detection of GRB 250424A
- GRB 250424A: Skynet Optical Observations
- GRB 250424A: Kilonova-Catcher optical afterglow detection
- GRB 250419a: Continued Liverpool Telescope observations
- GRB 250419A: Liverpool Telescope optical upper limit
- GRB 250407A: GRBAlpha detection
- GRB 250404A / EP250404a: GRBAlpha detection