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').
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"
24656 results found.
- GRB 250331B: Enhanced Swift-XRT position
- GRB 250320C : SVOM detection of a burst through offline search
- LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
- GRB 250330A: VLT/FORS2 Afterglow Detection
- GRB20250327B: 45th Parallel Observatory upper limit
- GRB 250328A: Swift/UVOT Detection
- GRB 250328A: Swift-XRT refined Analysis
- Fermi-LAT gamma-ray observations of IceCube-250330A
- 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 250331C: Swift detection of a burst
- GRB 250331B: Swift detection of a burst
- GRB 250331A: MAXI/GSC detection
- SVOM/sb25033102: SVOM detection of an X-ray transient
- LIGO/Virgo/KAGRA S250331o: Identification of a GW compact binary merger candidate
- 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: VLT/FORS2 Optical Observations
- GRB 250329B: Swift-XRT afterglow detection
- GRB 250330A: Swift detection of a burst
- GRB 250329B: SVOM/C-GFT optical upper limit
- LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 1)
- 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 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 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: LCO optical counterpart detection
- GRB 250328A: SVOM detection of a burst
- 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: 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 250327A: Swift-XRT refined Analysis
- 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: DDOTI Optical Observations
- GRB 250327A: COLIBRÍ optical upper limit
- LIGO/Virgo/KAGRA S250326y: Updated Sky localization
- 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
- 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
- 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)
- SVOM/sb25032302: SVOM detection of a long X-ray transient
- GRB 250322B: AstroSat CZTI detection of a bright long burst
- 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
- 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: COLIBRÍ Continuing Optical Observations
- EP250321a: WFST optical observations