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"
18399 results found.
- GRB 250407A: SRG/ART-XC afterglow detection
- LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
- IPN triangulation of GRB 250406B (short/hard)
- GRB 250331D: Swift-XRT afterglow detection
- GRB 250403A: Montarrenti Observatory optical detection
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250331C Swift-BAT refined analysis
- GRB 250331B Swift-BAT refined analysis
- GRB 250330A Swift-BAT refined analysis
- EP250321A: J band upper limit by SYSU 80cm telescope
- GRB 250403A: Swift/UVOT Detection
- GRB 250402A: Swift/UVOT Upper Limits
- GRB 250403A: LCO optical counterpart detection
- GRB 250402A: EP-FXT afterglow detection
- GRB 250403A: Swift-XRT observations
- GRB 250402A: Swift-XRT observations
- GRB 250225B: VLT host galaxy redshift z = 0.950
- 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
- GRB250331D: AbAO optical observations
- GRB 250331D: Fermi GBM observation
- GRB 250331C: Swift/UVOT Upper Limits
- GRB 250331B: Swift/UVOT Upper Limits
- GRB 250331D: Swift-XRT observations
- GRB 250331C: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- GRB 250331B: Swift-XRT refined Analysis
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
- GRB 250327A Swift-BAT refined analysis
- GRB 250329B: CAHA 2.2m telescope optical limit
- GRB 250331D: Swift ToO observations
- Swift GRB 250331C: Global MASTER-Net observations report
- Swift GRB 250331B: Global MASTER-Net observations report
- GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
- GRB 250331C: Enhanced Swift-XRT position
- GRB 250331B: Enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250329B: Swift-XRT confirmation of fading
- GRB20250327B: 45th Parallel Observatory upper limit
- GRB 250328A: Swift/UVOT Detection
- GRB 250328A: Swift-XRT refined Analysis
- GRB 250330A: Fermi GBM Observation
- GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331C: Prompt enhanced Swift-XRT position
- GRB 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- GRB 250330A: SVOM/VT optical upper limit
- GRB 250330A: BOOTES-7 early optical upper limit
- GRB 250330A: Swift/UVOT Upper Limits
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250330A: Fermi GBM Final Localization
- GRB 250330A: Prompt Swift-XRT position
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- Swift GRB250330.26: Global MASTER-Net observations report
- GRB 250329B: SVOM/C-GFT optical upper limit
- GRB 250329B: SVOM/VT optical upper limit
- GRB 250329A: Swift-XRT afterglow detection
- GRB 250328A: SVOM/C-GFT optical upper limit
- GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
- GRB 250327B: LCO optical counterpart detection
- GRB 250322A: GRANDMA/TNOT optical upper limits
- 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
- FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
- GRB 250327A: J-band observations with WINTER
- GRB 250327A: SVOM/VT optical candidate
- GRB 250327A: Fermi GBM observation
- Swift GRB 250327A: Global MASTER-Net observations report
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- GRB 250327A: Swift detection of a burst
- Konus-Wind detection of GRB 250322A (short)
- IPN triangulation of GRB 250322B
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- GRB 250322A: Swift-BAT refined analysis
- GRB 250322A: Swift/UVOT Upper Limits
- GRB 250321B: Swift-XRT observations
- GRB 250322A: Swift-XRT refined Analysis
- GRB 250322A: AstroSat CZTI detection of a short burst
- GRB250322A: STEP/T80S optical limits
- GRB 250322A: VLT optical observations
- GRB 250322A: VLT near-infrared observations
- GRB 250322A: NOT optical upper limits
- GRB 250322A: Enhanced Swift-XRT position
- GRB 250322A: MASTER optical observation
- GRB 250322A: Swift detection of a short burst
- EP250321a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250225B: GECAM-A detection
- GRB 250312A: GECAM-A detection
- GRB 250321B: Swift ToO observations
- GRB 250321A: Swift-BAT refined analysis
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250320B: Fermi-LAT detection
- GRB 250321A: Swift/UVOT Upper Limits