Radio Emission from the Magnetically Active M Dwarf UV Ceti from 1 to 105 GHz

Abstract

Abstract BL and UV Ceti are a nearby (2.7 pc) binary system with similar masses, spectral types, and rapid rotation rates, but very different magnetic activity. UV Ceti’s much stronger large-scale magnetic field may cause this difference, highlighting key unanswered questions about dynamo processes in fully convective objects. Here, we present multiepoch characterization of the radio spectrum of UV Ceti spanning 1–105 GHz, exhibiting flared emission similar to coronal activity, auroral-like emission analogous to planetary magnetospheres, and slowly varying persistent emission. Radio observations are a powerful means to probe the role that the large-scale magnetic field of UV Ceti has in nonthermal particle acceleration because radio-frequency phenomena result from both the activity of small-scale field features as well as large-scale auroral current systems. We find temporal variability at all bands observed, and a hint of rotational modulation in the degree of circular polarization up to 40 GHz. The persistent component of the emission is fairly constant from 1 to 105 GHz, making optically thick emission or optically thin gyrosynchrotron from electrons with an isotropic pitch angle distribution unlikely. We discuss the possibility of emission mechanisms analogous to Jupiter’s radiation belts.