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"
17213 results found.
- GRB 250322A: third epoch of NOT optical observations
- 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 250321B: Swift-XRT observations
- EP250321a: TNOT Observation of Optical Counterpart
- FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
- SVOM/sb25032302: SVOM detection of a long X-ray transient
- GRB250322A: STEP/T80S optical limits
- 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
- GRB 250321B: Swift ToO observations
- EP250321a: WFST optical observations
- EP250321a: Xinglong 216 decaying optical observations
- GRB 250321A: Swift-XRT refined Analysis
- GRB 250321B: SVOM detection of a sub-threshold transient event
- 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: COLIBRÍ Optical Observations
- EP250321a: REM optical/NIR afterglow detection
- EP250321a: TRT optical counterpart detection
- 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: Swift detection of a burst
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
- 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 250317B: OHP/T193 optical observations
- GRB250312A: Swift/UVOT Upper Limits
- GRB 250317B: REM optical/NIR 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: Swift ToO observations
- EP250315a: refined analysis of the EP-WXT and EP-FXT observations
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250314A: Swift XRT Detection
- EP250315a: optical counterpart candidate detected by Gemini North
- EP250315a: Einstein Probe detection of an X-ray transient
- 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
- GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
- GRB 250314A: SVOM detection of a burst
- GRB 250313A: Swift ToO observations
- EP250304a: Pan-STARRS r and i-band imaging and photometry
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
- GRB 250312A: Enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
- GRB 250312A: Swift detection of a burst
- GRB 241213A: VIRT Optical Upper Limit
- GRB 241228A: VIRT Optical Upper Limit
- GRB 250311A/EP250311a: Optical upper limits with Kinder observations
- GRB 230509B: 1.3m DFOT Optical observations
- GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
- GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
- GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
- GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
- GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250309B: PRIME near-infrared detection
- EP250304a: Chandra detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A/EP250311a: TRT optical upper limit
- GRB 250311A: Tiled Swift observations
- EP250311a/GRB 250311A: EP-WXT detection