GCN Circulars
GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"26057 results found.
- 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 250317B: OHP/T193 continued follow-up
- GRB 250317B: Mondy AZT-33IK Optical Observations
- GRB 250317B: NOT optical observations suggest an optical plateau phase
- GRB 250317B: GTC/OSIRIS+ spectroscopic redshift z=3.44
- 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
- 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 250316A: Fermi GBM Observation
- GRB 250316A: Swift-XRT observations
- 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 250314A: EP-FXT afterglow detection
- GRB 250314A: Swift/UVOT Upper Limits
- GRB 250312B: GRBAlpha detection
- GRB 250314A: Swift XRT Detection
- SVOM/MXT upper limit on GRB 250314A
- GRB 250314A: NOT near-infrared candidate counterpart
- GRB 250312B: Fermi GBM Observation
- GRB 250313A: Swift-XRT observations
- Konus-Wind detection of GRB 250308A
- GRB 250313A: Fermi-LAT detection
- GRB 250313A: Swift ToO observations
- GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
- EP250304a: SVOM/VT optical observation
- ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
- EP250302a: Chandra X-ray Detection
- GRB 250312A: Swift-XRT refined Analysis
- GRB 250312A: Enhanced Swift-XRT position
- LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
- GRB 250226B: Fermi GBM Observation
- Swift GRB 250312A: Global MASTER-Net observations report
- GRB 250302A: Fermi GBM Observation
- GRB 250312A: Swift detection of a burst
- GRB 241213A: VIRT Optical Upper Limit
- GRB 241228A: VIRT Optical Upper Limit
- GRB 250223B: Fermi GBM Observation
- GRB 250311A: Swift-XRT observations
- GRB 250228A: Fermi GBM Observation
- GRB 250309B: 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
- EP250304a: Chandra detection
- GRB 250225B: Swift-BAT refined analysis
- GRB 250311A: Tiled Swift observations
- IPN triangulation of GRB 250308A (short)
- IPN triangulation of GRB 250309B
- GRB 250309B: Swift-XRT refined Analysis
- GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
- Liverpool Telecope observations of AT 2025dws / GRB 250309B
- GRB 250309B / AT2025dws: SAO RAS optical observations
- GRB 250309B / AT2025dws: Swift-UVOT detection
- AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
- GRB250309B: One candidate counterpart from the Zwicky Transient Facility
- Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
- GRB 230509B: Tiled Swift observations
- GRB 250306A: EIRSAT-1 GMOD detection
- Konus-Wind detection of GRB 250306A
- GRB 250306A: Swift-BAT refined analysis
- GRB 250306A: NuSTAR detection of the prompt emission
- GRB 250306A: AstroSat CZTI detection
- Swift GRB 250306A: Global MASTER-Net observations report
- GRB 250306A: Swift detection of a burst
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- EP250302A: 1.3m DFOT optical afterglow detection
- EP250304a: REM NIR upper limits
- IPN triangulation of GRB 250222A
- EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
- EP250304a: Swift-XRT detection of a fading X-ray source
- LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
- EP250302a: Swift/UVOT detection
- EP250302a: NUTTelA-TAO Early Measurments
- EP250302a: REM NIR upper limits
- EP250302a: Xinglong F60B optical observation
- EP250302a: Swift-XRT observations of a fading X-ray source
- GRB 250226A: GRANDMA Optical Observations
- GRB 250225B: VLT near-infrared afterglow confirmation
- EP250228a: Optical observations with Kinder and Swift/UVOT
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250225B: VLT/HAWKI near-infrared observations
- EP250228a: updates on the EP observations
- EP250223a: J band upper limit by SYSU 80cm telescope
- EP250228a: Swift/XRT localisation
- GRB 250226A / EP250226a: LCO detection of the afterglow