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').
19136 results found.
- GRB 250314A: VLA detection
- Fermi GRB 250330B: Global MASTER-Net observations report
- Fermi GRB 250330A: Global MASTER-Net observations report
- GRB 250330A: BOOTES-7 early optical upper limit
- GRB 250330A: Swift/UVOT Upper Limits
- GRB 250330A: Swift-XRT afterglow detection
- GRB 250328A: 1.6m Mephisto optical observations
- IceCube Alert 250330.35: Global MASTER-Net observations report
- GRB 250330A: VLT/FORS2 Optical Observations
- Swift GRB250330.26: Global MASTER-Net observations report
- GRB 250329B: SVOM/C-GFT optical upper limit
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
- GRB 250327B: ALMA detection
- GRB 250327B: VLA detection
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- GRB250329A: REM optical afterglow detection
- GRB 250329B: GWAC-F50A optical upper limit
- GRB 250328A: SVOM/VT optical observation
- GRB 250329A: Fading optical counterpart detection by LCO.
- GRB 250328A: SVOM/C-GFT optical upper limit
- GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
- GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: J-band observations with WINTER
- GRB 250327B: LCO optical counterpart detection
- GRB 250328A: GWAC-F50A optical upper limit
- FRB 20250316A: FTW optical observations
- LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
- GRB 250327B: further optical observations by LCOGT
- GRB 250327b: Liverpool Telescope optical observations
- GRB 250327A: SVOM/VT upper limits on the XRT position
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250327B: 1.6m Mephisto optical observations
- GRB 250327B: GOTO optical counterpart detection
- GRB 250327B: SAO RAS optical candidate
- FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
- FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
- GRB 250327A: J-band observations with WINTER
- FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
- Fermi GRB 250327A: Global MASTER-Net observations report
- Swift GRB 250327A: Global MASTER-Net observations report
- GRB 250327A: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- Fermi trigger No 764700395: Global MASTER-Net observations report
- 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 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
- GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
- GRB 250321B: Swift-XRT observations
- FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
- GRB 250322A: Gemini-North redshift of candidate host galaxy
- EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
- GRB250322A: STEP/T80S optical limits
- GRB 250322A: Gemini-South optical observations
- GRB 250322A: VLT optical observations
- GRB 250322A: VLT near-infrared observations
- FRB 250316A: DDOTI Continued Optical Observations
- GRB 250322A: NOT optical upper limits
- 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
- GRB 250322A: MASTER optical observation
- EP250321a: Liverpool Telescope optical follow-up
- EP250321a: Mondy AZT-33IK Optical Observations
- 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: KAIT optical observations
- EP250321A: COLIBRÍ Continuing Optical Observations
- GRB 250321B: Swift ToO observations
- EP250321a: WFST optical observations
- EP250321a: Xinglong 216 decaying optical observations
- EP250321a: SVOM/VT optical observation
- EP 250321A: Optical counterpart detection by LCO.
- EP250321a: Kinder optical follow-up observations
- GRB 250321A: Swift/UVOT Upper Limits
- EP250321a: LCO optical counterpart detection
- EP250321A: COLIBRÍ Optical Observations
- EP250321a: VLT/X-shooter redshift z = 4.368
- EP250321a: REM optical/NIR afterglow detection
- Fermi GRB 250320B: Global MASTER-Net observations report
- 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 250314A: Keck/NIRC2 J-band upper limit
- EP250226a/GRB 250226A: KAIT optical observations
- GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
- GRB 250317B: Mondy AZT-33IK Continued Optical Observations
- Fermi GRB 250319B: Global MASTER-Net observations report
- 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