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"
23838 results found.
- EP250416a: Swift/XRT counterpart fading
- EP250416a: refined EP-WXT and EP-FXT analysis
- EP20250416a: Swift/XRT counterpart detection
- IceCube-250416A: DDOTI Optical Observations
- SVOM/sb25041603 is not a GRB
- EP250416a: GSP optical upper limit
- EP250416a: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
- IceCube-250416A: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
- GRB 250416B: Fermi GBM Final Real-time Localization
- GRB 250416A: Fermi GBM Final Real-time Localization
- SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
- SVOM/sb25041603: SVOM detection of an X-ray transient
- Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
- IceCube 250414.324: DDOTI Optical Observations
- EP250304a: ATCA radio observations
- GRB 250412A: AstroSat CZTI detection
- 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
- GRB 250411A: DDOTI Optical Observations
- Fermi GRB 250411A: Global MASTER-Net observations report
- GRB 250411A: Fermi GBM Final Real-time Localization
- GRB 250407A: Mondy and AbAO Optical Observations
- EP250227a: Further NOT optical observations
- IceCube-250406A: Swift-XRT observations
- IPN triangulation of GRB 250407A
- EP250407a: Global MASTER-Net observations report
- GRB 250407A: LCO detection of a fading optical counterpart
- GRB 250407A: SVOM/GRM observation of a bright long burst
- GRB 250407A: EP-WXT afterglow detection
- EP250407a: EP-WXT detection of a fast X-ray transient
- GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250407A: Fermi GBM Detection
- Fermi GRB 250407A: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
- IceCube 250406A: DDOTI Optical Observations of the Refined Position
- IPN triangulation of GRB 250406B (short/hard)
- GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
- GRB 250407A: Fermi GBM Final Real-time Localization
- IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
- IceCube 250406.951: DDOTI Optical Observations
- IceCube Alert 250406.95: Global MASTER-Net observations report
- Fermi trigger No 765663719: Global MASTER-Net observations report
- Fermi GRB 250406A: Global MASTER-Net observations report
- GRB 250406A: Fermi GBM Final Real-time Localization
- EP250404a / GRB 250404A: Montarrenti Observatory optical observations
- Fermi trigger No 765619921: Global MASTER-Net observations report
- Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
- EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
- GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
- GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
- EP250402a: Optical upper limit with PD 1.3m observations
- GRB 250404A / EP250404a: NOT optical observations
- GRB 250331D: Swift-XRT afterglow detection
- EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
- EP250404a: REM optical/NIR observations
- EP250404A: COLIBRÍ/DDRAGO Optical Observations
- EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
- EP250404a: LCO optical counterpart detection
- Fermi GRB 250404A: Global MASTER-Net observations report
- EP250404a: Xinglong decaying optical counterpart
- GRB 250404A: Fermi GBM Detection
- EP250404a: Global MASTER-Net observations report
- GRB 250403A: KAIT optical observations
- EP250404a: AKO Optical Afterglow Detection
- GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250403A: Fermi GBM observations
- EP250404a: Mephisto multi-band optical detection
- 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
- EP250404a: Nanshan/HMT optical counterpart detection
- GRB 250404A: Fermi GBM Final Real-time Localization
- EP250402a: Optical upper limit with Kinder observations
- GRB 250403A: REM NIR afterglow detection
- IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
- GRB 250403A: JinShan optical observations
- GRB 250403A: Optical counterpart detection by LCO.
- EP250402a: EP-FXT follow-up observations
- GRB 250403A: Swift-XRT observations
- Fermi GRB 250403A: Global MASTER-Net observations report
- GRB 250402A: NUTTelA-TAO Early Optical Limits
- GRB 250403A: GMG Optical Observation
- GRB 250403A: 1.6m Mephisto multi-band optical detection
- GRB 250402A: Fermi GBM Observation
- GRB 250403A: SVOM/C-GFT optical observations
- GRB 250403A: GOTO detection of the optical afterglow
- GRB 250402A: Swift-XRT observations
- GRB 250403A : SVOM detection of a burst
- GRB 250403A: Fermi GBM Final Real-time Localization
- GRB 250225B: VLT host galaxy redshift z = 0.950
- GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
- GRB 250402A: VLT/FORS2 spectroscopic redshift z = 2.823
- GRB 250402A: REM optical/NIR upper limits
- GRB 250402A: LCO optical counterpart detection
- GRB 250402A: refined SVOM/MXT data analysis
- The EP-WXT trigger 01709133862 is a flaring star