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"
18693 results found.
- GRB 250430A: Swift-XRT refined Analysis
- GRB 250430A: Swift/UVOT Detection
- GRB 250430A: Enhanced Swift-XRT position
- GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
- GRB 250430A: DDOTI Optical Observations
- GRB 250430A: Leavitt Observatory optical upper limit
- GRB 250430A: Bassano Bresciano Observatory upper limit
- GRB 250430A : MITSuME Akeno optical upper limits
- 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
- GRB 250430A: Swift detection of a burst with optical counterpart
- Swift GRB250430.73: Global MASTER-Net observations report
- GRB 250427A: Swift/UVOT Detection
- EP250427a: EP-FXT follow-up observations
- GRB 250427A: Swift-XRT refined Analysis
- GRB 250424A: LCO optical observation
- GRB 250424A: Swift-BAT refined analysis
- GRB 250424A: SVOM/GRM observation of a long burst
- 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 250424A: Swift-XRT refined Analysis
- GRB 250424A: Enhanced Swift-XRT position
- GRB 250424A: AstroSat CZTI detection of a bright long burst
- GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
- GRB 250424A: BlackGEM optical afterglow detection
- GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
- GRB 250424A: likely host galaxy
- GRB 250424A: DDOTI Afterglow Detection
- GRB 250424A: REM optical/NIR afterglow detection
- GRB 250424A: Swift detection of a burst with an optical counterpart
- Swift GRB250424A: Global MASTER-Net observations report
- Swift GRB250424A: Global MASTER-Net OT detection
- SVOM/sb25042207: XRT observations
- EP250421a: NOT optical observations
- EP250421a: Swift/XRT counterpart detection
- GRB 250419A: Swift/UVOT Follow up
- GRB 250419A: LCO optical afterglow multi-band observations
- GRB 250419A: Mondy and AbAO Optical Observations
- GRB 250419A: Swift-XRT localisation
- GRB 250419A: Swift-XRT refined Analysis
- EP250416a: Swift/XRT counterpart fading
- EP20250416a: Swift/XRT counterpart detection
- GRB 250407A: Mondy and AbAO Optical Observations
- IceCube-250406A: Swift-XRT observations
- IPN triangulation of GRB 250407A
- GRB 250407A: LCO detection of a fading optical counterpart
- EP250407a: Swift-XRT observations
- Konus-Wind detection of GRB 250407A
- GRB 250407A: SVOM/GRM observation of a bright long burst
- GRB 250407A: EP-WXT afterglow detection
- GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250407A: Fermi GBM Detection
- GRB 250407A: Swift-XRT afterglow detection
- GRB 250407A: Swift ToO observations
- 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