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').
- SVOM/sb25033102 is a false trigger
- GRB 250330A: Fermi GBM Observation
- GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
- GRB 250331D: Fermi GBM Final Real-time Localization
- GRB 250331C: Prompt enhanced Swift-XRT position
- GRB 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- GRB 250330A: SVOM/VT optical upper limit
- GRB 250331A: MAXI/GSC detection
- SVOM/sb25033102: SVOM detection of an X-ray transient
- GRB 250314A: VLA detection
- LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
- Fermi GRB 250330B: Global MASTER-Net observations report
- GRB 250330B: Fermi GBM Final Real-time Localization
- 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
- GRB 250329B: SVOM/COLIBRÍ (F-GFT) optical upper limit
- GRB 250330A: Fermi GBM Final Localization
- IceCube-250330A - IceCube observation of a high-energy neutrino candidate track-like event
- IceCube Alert 250330.35: Global MASTER-Net observations report
- GRB 250330A: VLT/FORS2 Optical Observations
- GRB 250330A: Prompt Swift-XRT position
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- Swift GRB250330.26: Global MASTER-Net observations report
- GRB 250328A: A fading optical afterglow confirmed by SVOM/VT
- 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 250329B: SVOM/VT optical upper limit
- GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
- GRB 250329B: 1.6m Mephisto Optical Upper Limits
- LIGO/Virgo/KAGRA S250329fl: 2 counterpart neutrino candidate events from an IceCube neutrino search
- GRB250329A: REM optical afterglow detection
- GRB 250329B: GWAC-F50A optical upper limit
- GRB 250329B: SVOM detection of a faint transient
- GRB 250329A: Swift-XRT afterglow detection
- 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: 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