Overview

• Detected on March 16, 2025, FRB 20250316A—nicknamed RBFLOAT—originates about 130 million light-years away in the spiral galaxy NGC 4141 in Ursa Major.
• This marks the first FRB localized with the completed CHIME plus Outriggers system, which used very long baseline interferometry to reach tens of milliarcseconds precision, or roughly 13 parsecs.
• The burst’s position lies on the outskirts of a star-forming region rather than its core, providing key context for interpreting the local environment.
• A search of six years of CHIME data found no previous bursts from this location, indicating a one-off event within that archive and informing the debate over repeating versus nonrepeating sources.
• The collaboration reports the result in Astrophysical Journal Letters, with follow-up observations including MMT and JWST and a pivotal role for the NSF Green Bank Outrigger.