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"
24592 results found.
- GRB 250327A: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250326y: Updated Sky localization
- IPN triangulation of GRB 250322B
- LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
- EP250321a: Mondy AZT-33IK Continued Optical Observations
- Swift follow-up observations of FRB250316A and EP J120944.2+585060
- GRB 250322A: third epoch of NOT optical observations
- GRB 250322A: Swift-BAT refined analysis
- GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
- FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
- GRB 250322A: further NOT optical observations
- EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
- GRB 250322A: Swift/UVOT Upper Limits
- EP250324A: COLIBRÍ/DDRAGO Optical Observations
- FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
- GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
- GRB 250321B: Swift-XRT observations
- GRB 250322A: Swift-XRT refined Analysis
- EP250321a: TNOT Observation of Optical Counterpart
- FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
- SVOM/sb25032302: SVOM detection of a long X-ray transient
- GRB 250322B: AstroSat CZTI detection of a bright long burst
- GRB 250322A: VLT optical observations
- GRB 250322A: VLT near-infrared observations
- FRB 250316A: DDOTI Continued Optical Observations
- GRB 250322A: NOT optical upper limits
- GRB 250322A: Enhanced Swift-XRT position
- GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
- EP250321a: Liverpool Telescope optical follow-up
- 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: refined analysis of the EP-WXT and EP-FXT observations
- EP250321A: COLIBRÍ Continuing Optical Observations
- EP250321a: WFST optical observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- 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
- EP 250321A: Optical counterpart detection by LCO.
- EP250321a: Kinder optical follow-up observations
- GRB 250321A: Swift/UVOT Upper Limits
- GRB 250320B: SVOM/GRM observation of a long burst
- EP250321a: LCO optical counterpart detection
- EP250321a: Swift-XRT detection of an X-ray source
- EP250321A: COLIBRÍ Optical Observations
- GRB 250320B: AstroSat CZTI detection
- EP250321a: REM optical/NIR afterglow detection
- EP250321a: TRT optical counterpart detection
- Swift GRB 250321A: Global MASTER-Net observations report
- EP250321a: Einstein Probe detection of an X-ray transient
- GRB 250321A: GOTO optical upper limits
- 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 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
- LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
- GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
- GRB 250317D: EIRSAT-1 GMOD Detection
- LIGO/Virgo/KAGRA S250319bu: Updated Sky localization
- GRB 250314A: ATCA radio upper limits
- GRB 250317B: OHP/T193 continued follow-up
- LIGO/Virgo/KAGRA S250319bu: Identification of a GW compact binary merger candidate
- GRB 250317C: SVOM/GRM observation of a long burst
- GRB 250317B: Leavitt Observatory optical upper limit
- GRB 250317B: Mondy AZT-33IK Optical Observations
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317C: GECAM-B detection
- GRB 250317B: OHP/T193 optical observations
- 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
- GRB250317B: 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
- GRB 250314A: SVOM/GRM analysis
- GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
- GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
- GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
- GRB 250314A: EP-FXT afterglow detection
- EP250315a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
- GRB 250314A: Swift XRT Detection
- EP250315a: optical counterpart candidate detected by Gemini North