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').
- GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
- GRB 250329A: VLT/X-shooter redshift z = 2.921
- GRB 250329A: SVOM/VT optical counterpart confirmation
- GRB 250329A: SVOM detection of a burst
- GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
- GRB 250327B: J-band observations with WINTER
- GRB 250327B: MASTER detection of OT rebrightening
- GRB 250327B: LCO optical counterpart detection
- GRB 250328A: GWAC-F50A optical upper limit
- GRB 250328A: SVOM detection of a burst
- FRB 20250316A: FTW optical observations
- LIGO/Virgo/KAGRA S250328ae: NED Galaxies in the 4-Update Localization Volume
- EP250302a: SPI-ACS/INTEGRAL Upper Limit
- GRB 250327B: CrAO and SAO RAS Optical Observations
- GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
- GRB 250327B: further optical observations by LCOGT
- EP250315a: Pan-STARRS r and i-band imaging and photometry
- GRB 250327b: Liverpool Telescope optical observations
- GRB 250322A: GRANDMA/TNOT optical upper limits
- LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
- GRB 250327A: SVOM/VT upper limits on the XRT position
- LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
- GRB 250327B: Las Cumbres optical counterpart detection
- GRB 250327B: Swift-XRT detection of the X-ray afterglow
- GRB 250327B: 1.6m Mephisto optical observations
- GRB 250327B: NOT spectroscopic redshift z = 3.035
- GRB 250327A: Swift-XRT refined Analysis
- GRB 250327B: GOTO optical counterpart detection
- GRB 250327B: SVOM/VT optically bright counterpart
- GRB 250327B: SAO RAS optical candidate
- GRB 250327B: SVOM detection of a burst
- 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
- GRB 250327A: SVOM/VT optical candidate
- FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
- GRB 250327A: Fermi GBM observation
- 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
- GRB 250327A: Swift detection of a burst
- GRB 250327A: Fermi GBM Final Real-time Localization
- Fermi trigger No 764700395: Global MASTER-Net observations report
- LIGO/Virgo/KAGRA S250326y: Updated Sky localization
- Konus-Wind detection of GRB 250322A (short)
- 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
- The EP-WXT trigger 01709133021 (designated as EP250324a) is not a real source
- 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
- 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)
- GRB 250322A: Gemini-North redshift of candidate host galaxy
- EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
- SVOM/sb25032302: SVOM detection of a long X-ray transient
- GRB 250322A: AstroSat CZTI detection of a short burst
- GRB 250322B: AstroSat CZTI detection of a bright long burst
- 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 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
- GRB 250322A: MASTER optical observation
- 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: KAIT optical observations
- EP250321A: COLIBRÍ Continuing Optical Observations
- GRB 250225B: GECAM-A detection
- GRB 250312A: GECAM-A detection
- GRB 250321B: Swift ToO observations
- EP250321a: WFST optical observations
- GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
- GRB 250321C: Fermi GBM Final Real-time Localization
- 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