Electron Cyclotron Maser Emission as the Driving Mechanism in Long-Period Radio Transients

Abstract: Long-period radio transients (LPRTs) are highly polarised, coherent radio sources with periods of minutes to hours and bursts typically lasting 10-100s. We argue that electron cyclotron maser emission (ECME) explains their narrow duty cycles and polarisation properties. In this picture, a rotating oblique magnetosphere beams radiation into a thin, hollow emission cone whose surface lies almost perpendicularly to the local magnetic field. The observed very narrow pulses arise when the line of sight skims the cone. Broader profiles and weak leading or trailing components occur when multiple azimuths along the emission ring satisfy the maser resonance condition. The observed isotropic-equivalent luminosities of ~10^{30}-10^{31} erg s^{-1} correspond to modest intrinsic powers once strong ECME beaming is taken into account, which is readily achievable through accretion from the interstellar medium.