Starspots as the origin of ultrafast drifting radio bursts from an active M dwarf
Jiale Zhang, Hui Tian, S. Bellotti, Tianqi Cang, J. R. Callingham, H. K. Vedantham, Bin Chen, Sijie Yu, P. Zarka, Corentin Louis, Peng Jiang, H. Lu, Yang Gao, Jinghai Sun, Hengqian Gan, Hui Li, Chun Sun, Zheng Lei, Meng-Lin Huang
Abstract
Detecting coherent radio bursts from nearby M dwarfs provides opportunities for exploring their magnetic activity and interaction with orbiting exoplanets. However, it remains uncertain whether the emission is related to flare-like activity similar to the Sun or magnetospheric process akin to magnetized planets. Using observations (1.0 to 1.5 gigahertz) taken by the Five-hundred-meter Aperture Spherical radio Telescope, we found a type of millisecond-scale radio bursts with exceptionally high-frequency drift rates (~8 gigahertz per second) from an active M dwarf, AD Leo. The ultrafast drift rates point to a source region with a notably low magnetic scale height (<0.15 [Formula: see text] , [Formula: see text] as the stellar radius), a feature not expected in a commonly assumed dipole-like global field but highly possible in localized strong-field structures, i.e., starspots. Our findings suggest that a concentrated magnetic field above starspots could be responsible for some of the most intense radio bursts from M dwarfs, supporting a solar-like electron acceleration mechanism.