Overview

• CHIME’s new Outriggers enabled very long baseline interferometry that localized FRB20250316A to roughly 13 parsecs on a spiral arm of NGC 4141 about 130 million light-years away.
• The one-off burst, nicknamed RBFLOAT, is the brightest FRB yet recorded and was detected on March 16, 2025, in the constellation Ursa Major.
• Follow-up work reports a nearby infrared source resolved by the James Webb Space Telescope near the burst site, likely a red giant or massive middle-aged star that offers clues to the local environment.
• Searches of CHIME archives and more than 200 hours of targeted monitoring found no repeats, and optical facilities including KAIT, Keck, Gemini, and MMT detected no transient counterpart.
• The location just outside an active star-forming region is consistent with some magnetar scenarios but does not rule out alternative progenitors, and researchers expect many more precise localizations to test these models.