Résumé / Abstract Seminaire_IAP
« Fast radio bursts as precursor radio emission from monster shocks »

Arno Vanthieghem
Obs. Paris (Paris, France)

Fast radio bursts (FRBs) are short blasts of radio waves whose origins remain a mystery. They are ubiquitous across the sky, around a few thousand per day, and their extreme brightness bears witness to one of the most extreme coherent radiative phenomena in our Universe. Although several distinct origins are conceivable, there are indications that some of these bursts are associated with magnetars. When a magnetar’s crust breaks or quakes, a considerable amount of energy is transferred to the magnetosphere in the form of electromagnetic waves. Monster shocks belong to a class of shocks formed by the steepening of such waves, well within the magnetosphere. They are described as “monsters” because of the huge power they carry.

Motivated by these considerations, I will discuss a series of recent studies on the steepening and dissipation of a strongly magnetized fast magnetosonic wave propagating in a dipolar background magnetic field, using kinetic simulations that encompass MHD scales. Our analysis confirms the formation of a monster shock that dissipates about half of the fast magnetosonic wave energy. It also reveals, for the first time, the self-consistent generation of a high-frequency precursor wave by a synchrotron maser instability at the monster shock front, carrying 0.1% of the total energy dissipated at the shock. The spectrum of the precursor wave exhibits several sharp harmonic peaks at GHz frequencies under conditions anticipated in magnetars. Such signals may appear as fast radio bursts
vendredi 22 mai 2026 - 11:00
Amphithéâtre Henri Mineur, Institut d'Astrophysique de Paris
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