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').
777 results found.
- GRB 250225B: GECAM-A detection
- GRB 250321B: Swift ToO observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- GRB 250320B: Fermi GBM Observation
- GRB 250320B: Fermi-LAT detection
- GRB 250321B: SVOM detection of a sub-threshold transient event
- EP250321a: SVOM/VT optical observation
- GRB 250320B: SVOM/GRM observation of a long burst
- GRB 250314A: Keck/NIRC2 J-band upper limit
- GRB 250313A: GRBAlpha detection
- 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: GTC/OSIRIS+ spectroscopic redshift z=3.44
- GRB 250317B: REM optical/NIR observations
- GRB 250317B: Swift-XRT observations
- GRB 250314A: REM optical/NIR upper limits
- EP 250317B: Fading optical counterpart detection by LCO
- GRB 250317B: LCO detection of the fading optical afterglow
- GRB 250317B: refined SVOM/MXT analysis
- 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 250314A: SVOM/GRM analysis
- 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 250314A: Swift XRT Detection
- GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
- 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
- GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
- Konus-Wind detection of GRB 250313A
- Konus-Wind detection of GRB 250308A
- GRB 250314A: SVOM detection of a burst
- GRB 250313B: SVOM/GRM observation of a soft bright short burst
- GRB 250313A: SVOM/GRM observation of a bright long burst
- EP250304a: SVOM/VT optical observation
- GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
- GRB 250308A: CALET Gamma-Ray Burst Monitor detection
- GRB 250311B: SVOM detection of a burst
- GRB 250309B: SVOM/VT optical observation
- IPN triangulation of GRB 250308A (short)
- GRB 250308A: SVOM/GRM detection of QPO in the tail emission
- GRB 250308A: SVOM/GRM observation of a bright short burst
- GRB 250305A: AstroSat CZTI detection
- GRB 250305A: SVOM/GRM observation of a burst
- GRB 250219A: SVOM/C-GFT optical upper limit at early phase
- Konus-Wind detection of GRB 250222A
- IPN triangulation of GRB 250222A
- EP250302a: SVOM/VT optical observation
- EP250302a: Xinglong F60B optical observation
- EP250302a: SVOM/C-GFT optical observations
- GRB 250225B: EIRSAT-1 GMOD Detection
- GRB 250226A: Fermi GBM Observation
- GRB 250225B: INTEGRAL SPI-ACS detection
- EP250226a / GRB 250226A: SVOM/VT optical observations
- LIGO/Virgo/KAGRA S250206dm: Upper limits from SVOM/GRM Observations
- GRB 250225B: REM NIR upper limits
- Konus-Wind detection of GRB 250225B
- GRB 250225B: SVOM/GRM observation of a long burst
- GRB 250214A: SVOM/GRM observation
- GRB 250223C: SVOM/GRM observation of a long burst
- GRB 250219A: EP-FXT afterglow detection
- GRB 250222A: SVOM/GRM observation of a burst
- GRB 250210A: VZLUSAT-2 detection
- EP250223a: SVOM/VT optical observation
- GRB 250219A: NUTTelA-TAO / BSTI Optical Limits
- GRB 250219A: GRANDMA/Kilonova-Catcher upper limits
- SVOM trigger sb25022102 is not an astrophysical event
- SVOM/sb25022102: SVOM detection of an X-ray transient
- Konus-Wind detection of GRB 250217C (short)
- GRB 250219A: Swift/UVOT Upper Limits
- GRB 250219A: NOT optical observations
- GRB 250219A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
- GRB 250219A: 1.6m Mephisto optical upper limits
- GRB 250219A: SVOM/VT optical counterpart
- GRB 250219A: Swift-XRT observations
- GRB 250219A: Swift ToO observations
- GRB 250219A: SVOM detection of a burst
- Konus-Wind detection of GRB 250215A / EP250215a
- SVOM/sb25021804: COLIBRÍ/DDRAGO Confirmation of Variability
- SVOM/sb25021804: QSO variability in Liverpool Telescope observations
- GRB 250217C: SVOM/GRM observation
- GRB 250215A / EP250215A: Encouraging Follow-up Observations of a BdHN I with a Rest-Frame Duration 2.3 s at z=4.61
- Transient SVOM/sb25021804: COLIBRÍ/DDRAGO Optical Upper Limits on the Optical Counterpart
- SVOM/sb25021804: SVOM detection of a long X-ray transient
- GRB 250213A: Swift-XRT observations
- GRB 250215A / EP250215a: LCO detection of the afterglow
- EP250215a / GRB 250215A : GTC redshift z = 4.61
- GRB 250215A: Fermi GBM Observation
- GRB 250213A: COLIBRÍ/DDRAGO Optical Upper Limits on the Afterglow
- GRB 250215A: SVOM/GRM observation
- GRB 250215A / EP250215a: SVOM/VT optical candidate comfirmation
- GRB 250213A：SVOM/VT optical candidate
- GRB 250213A: Swift ToO observations