Low-frequency Radio Transients on the Active M-dwarf EQ Peg and the Search for Coronal Mass Ejections

Abstract

Abstract Stellar coronal mass ejections (CMEs) remain observationally elusive, but could have important implications for exoplanet habitability. Low-frequency radio bursts, known as Type IIs in the solar context, offer the best means to identify stellar CMEs, determine their occurrence rates, and characterize their properties. We report on 44 hr of observation of the nearby, magnetically active, and well-characterized M-dwarf star binary EQ Peg. The observations are taken with the Jansky Very Large Array’s P-band (230–470 MHz) receiver in both its B and C configurations. Two radio transient events were detected, one in each configuration. Both bursts lasted on the order of 20 minutes between 275 and 350 MHz, had a median polarization of ∼30%, and have a frequency drift rate of ∼10 kHz. These two events are likely not type II bursts as their properties do not match expected parameters based on coronal models for each star. This work and the work of Crosley & Osten represent a combined 64 hr for the longest timescale search of a single star for radio transients at low frequencies to date, and casts serious doubt on the assumption that a high flaring rate corresponds to a high rate of CMEs.