Abstract
ABSTRACT High brightness temperature radio transients such as pulsars and fast radio bursts (FRBs) require the coherent radiation of particles. The antenna class of coherent radiation models require a large number of charged particles radiating in phase, therefore the particles must be spatially confined and have well-aligned velocities. Given these necessary conditions, we look at the magnetic field induced by the currents associated with coherently emitting accelerated particles and consider the interaction between the radiating particles and the induced magnetic field. We find a maximum luminosity of coherent curvature radiation that depends on source parameters such as surface magnetic field and neutron star spin period. We find that coherent radio emission across all luminosities can be explained by coherent curvature radiation and suggest it could be universally responsible for both FRBs and extreme galactic sources. Using the Crab Pulsar as an example, we constrain the emission parameters and origin of the most extreme nanoshots to within 60 km of the pulsar surface assuming coherent curvature radiation. In agreement with recent observations, we also predict simultaneous X-ray emission from small-scale particle gyration due to the induced field.
Highlights
Coherent radiation is required for luminous, short duration radio transients, where the high brightness temperature cannot be explained by relativistic beaming alone (Pietka et al 2015; Melrose 2017)
In this Letter we have considered electrodynamic interactions between coherently radiating particles
This limit suggests that if the giant pulses are powered by coherent curvature radiation, they must originate in the inner magnetosphere very close to the neutron star (NS) surface
Summary
Coherent radiation is required for luminous, short duration radio transients, where the high brightness temperature cannot be explained by relativistic beaming alone (Pietka et al 2015; Melrose 2017). Coherent curvature radiation has been used to explain high brightness temperature emission from pulsars (Sturrock 1971; Ruderman & Sutherland 1975; Yang & Zhang 2018) This model has become one of the front-running radiation models of FRBs, where the conditions for the coherent emission of a large number of particles are found in the inner magnetospheres of highly-magnetized neutron stars known as magnetars (Katz 2016; Cordes & Wasserman 2016; Kumar et al 2017; Ghisellini & Locatelli 2018).
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