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"
6094 results found.
- EP250508a: Gemini NIR upper limits
- GRB 250510B: Fermi GBM Observation
- GRB 250510A: Swift-XRT observations
- GRB 250509A: Fermi GBM Observation
- IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
- GRB 250509A: Swift-XRT refined Analysis
- GRB 250506A: Swift-XRT afterglow detection
- GRB 250507A: Swift-XRT refined Analysis
- GRB 250506A: Swift/UVOT Upper Limits
- EP#01709175213/IGR J19566+0326: Swift-XRT detection
- GRB 250507A: refined SVOM/MXT data analysis
- GRB 250506A: Swift-XRT observations
- Fermi-LAT Gamma-ray Observations of IceCube-250506A
- EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
- GRB 250506A: Mephisto optical upper limits
- 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: Fermi GBM Observation
- GRB 250506A: Swift XRT observations and possible counterpart detection
- GRB 250504A: Swift-XRT refined Analysis
- GRB 250504A: Fermi GBM Observation
- GRB 250502A: Swift-XRT afterglow detection
- GRB 250502A: LCO optical counterpart detection
- Fermi-LAT Gamma-ray Observations of IceCube-250429A
- GRB 250430A: Swift-XRT refined Analysis
- GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
- GRB 250430A: NUTTelA-TAO Early Measurements
- EP250428b: refined analysis of the EP-FXT follow-up observation
- EP250428b: SAO RAS optical upper limit
- GRB 250427A: Swift/UVOT Detection
- Fermi-LAT Gamma-ray Observations of IceCube-250426A
- EP250427a: EP-FXT follow-up observations
- GRB 250427A: Swift-XRT refined Analysis
- Konus-Wind detection of GRB 250424A
- Fermi-LAT gamma-ray observations of IceCube-250421A
- GRB 250424A: Swift-XRT refined Analysis
- GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
- SVOM/sb25042207: XRT observations
- GRB 250419A: Optical Observations via Virtual Telescope Project
- EP250421a: Swift/XRT counterpart detection
- EP250421a: Mephisto optical counterpart confirmation
- The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
- GRB 250419A: LCO optical afterglow multi-band observations
- Fermi-LAT Gamma-ray Observations of IceCube-250416A
- GRB 250407A: rest-frame energetics from Konus-Wind observation
- GRB 250419A: Swift-XRT refined Analysis
- EP250416a: Swift/XRT counterpart fading
- Konus-Wind detection of GRB 250403A
- EP20250416a: Swift/XRT counterpart detection
- SVOM/sb25041603 is not a GRB
- EP250227a: Further NOT optical observations
- IceCube-250406A: Swift-XRT observations
- GRB 250407A: LCO detection of a fading optical counterpart
- Fermi-LAT gamma-ray observations of IceCube-250406A
- EP250407a: Swift-XRT observations
- GRB 250407A: Fermi GBM Detection
- GRB 250407A: Swift-XRT afterglow detection
- Konus-Wind detection of GRB 250404A / EP250404a
- EP250404a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250331D: Swift-XRT afterglow detection
- EP250404a: LCO optical counterpart detection
- EP250404a: Xinglong decaying optical counterpart
- GRB 250404A: Fermi GBM Detection
- GRB 250403A: Fermi GBM observations
- EP250404a: Nanshan/HMT optical counterpart detection
- EP250402a: Optical upper limit with Kinder observations
- GRB 250403A: LCO optical counterpart detection
- EP250402a: EP-FXT follow-up observations
- GRB 250403A: Swift-XRT observations
- GRB 250402A: Fermi GBM Observation
- GRB 250402A: Swift-XRT observations
- GRB 250402A: LCO optical counterpart detection
- GRB 250402A: refined SVOM/MXT data analysis
- GRB 250329B: Swift/UVOT Upper Limit
- GRB 250327A: Swift/UVOT Upper Limits
- GRB 250331D: Fermi GBM observation
- GRB 250331D: Swift-XRT observations
- GRB 250331C: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
- Konus-Wind detection of GRB 250327B
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250328A: Swift-XRT refined Analysis
- Fermi-LAT gamma-ray observations of IceCube-250330A
- GRB 250330A: Fermi GBM Observation
- GRB 250331C: Prompt enhanced Swift-XRT position
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250330A: Prompt Swift-XRT position
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250327B: LCO optical counterpart detection
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327B: further optical observations by LCOGT
- GRB 250327A: SVOM/VT upper limits on the XRT position
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327A: Swift-XRT refined Analysis
- GRB 250327B: SVOM detection of a burst