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.
Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
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"38214 results found.
- GRB 250322A: MASTER optical observation
- EP250321a: Mondy AZT-33IK Optical Observations
- GRB 250322A: Swift detection of a short burst
- FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
- EP250321a: KAIT optical observations
- GRB 250225B: GECAM-A detection
- GRB 250312A: GECAM-A detection
- GRB 250321B: Swift ToO observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- GRB 250321C: Fermi GBM Final Real-time Localization
- GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
- GRB 250320B: Fermi GBM Observation
- EP250321a: Xinglong 216 decaying optical observations
- GRB 250321A: Swift-BAT refined analysis
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250320B: Fermi-LAT detection
- GRB 250321B: SVOM detection of a sub-threshold transient event
- EP 250321A: Optical counterpart detection by LCO.
- GRB 250321A: Swift/UVOT Upper Limits
- GRB 250320B: SVOM/GRM observation of a long burst
- EP250321a: LCO optical counterpart detection
- GRB 250320B: AstroSat CZTI detection
- EP250321a: REM optical/NIR afterglow detection
- Fermi GRB 250320B: Global MASTER-Net observations report
- EP250321a: TRT optical counterpart detection
- EP250321a: Global MASTER-Net observations report
- Swift GRB 250321A: Global MASTER-Net observations report
- Fermi GRB 250321A: Global MASTER-Net observations report
- GRB 250321A: GOTO optical upper limits
- GRB 250321A: Swift-XRT localisation
- GRB 250314A: Keck/NIRC2 J-band upper limit
- EP250226a/GRB 250226A: KAIT optical observations
- GRB 250321A: Fermi GBM Observation
- GRB 250321A: Swift detection of a burst
- GRB 250321A: Fermi GBM Final Real-time Localization
- GRB 250320B: Fermi GBM Final Real-time Localization
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- GRB 250320A: Fermi GBM Final Real-time Localization
- Fermi GRB 250319B: Global MASTER-Net observations report
- FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
- GRB 250313A: GRBAlpha detection
- GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
- GRB 250319B: Fermi GBM Final Localization
- GRB 250319A: Fermi GBM Final Localization
- GRB 250317D: EIRSAT-1 GMOD Detection
- GRB 250314A: ATCA radio upper limits
- GRB 250317B: OHP/T193 continued follow-up
- GRB 250317C: SVOM/GRM observation of a long burst
- GRB 250317B: Leavitt Observatory optical upper limit
- GRB 250309B/AT2025dws: further ATCA observations
- GRB 250317B: Mondy AZT-33IK Optical Observations
- GRB 250317C: AstroSat CZTI detection
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
- GRB 250317C: GECAM-B detection
- GRB 250317B: OHP/T193 optical observations
- Fermi trigger No 763933627: Global MASTER-Net observations report
- GRB250312A: Swift/UVOT Upper Limits
- GRB 250317B: REM optical/NIR observations
- GRB 250317B: Swift-XRT observations
- GRB 250316A: Swift/UVOT Upper Limits
- GRB 250314A: REM optical/NIR upper limits
- GRB 250316A: AbAO AS-32 Optical Upper Limit
- EP 250317B: Fading optical counterpart detection by LCO
- GRB 250316A: Swift-XRT afterglow detection
- GRB 250317B: LCO detection of the fading optical afterglow
- GRB 250317B: refined SVOM/MXT analysis
- GRB 250317B: SVOM/VT detection of an optical candidate from VHF data
- GRB 250317B: SVOM/F-GFT (COLIBRÍ) Detection of a Fading Optical Counterpart
- GRB 250317B: SVOM detection of a burst / correction to GRB name of GCN 39752
- GRB 250317B: SVOM detection of a burst
- GRB 250316A: Fermi GBM Observation
- GRB 250316A: Swift-XRT observations
- Fermi trigger No 763862734: Global MASTER-Net observations report
- GRB 250317A: Fermi GBM Final Real-time Localization
- Fermi GRB 250316A: Global MASTER-Net observations report
- GRB 250314A: SVOM/GRM analysis
- GRB 250316A: Swift ToO observations
- GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
- GRB 250316A: Fermi GBM Final Real-time Localization
- GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
- GRB 250314A: EP-FXT afterglow detection
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250312B: GRBAlpha detection
- GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
- GRB 250314A: Swift XRT Detection
- GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
- GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
- SVOM/MXT upper limit on GRB 250314A
- GRB 250314A: SVOM/VT upper limit
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250313A: Fermi GBM Detection
- GRB 250313A: CALET Gamma-Ray Burst Monitor detection
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- Konus-Wind detection of GRB 250313A
- Konus-Wind detection of GRB 250308A
- GRB 250314A: SVOM detection of a burst