Fast radio bursts by stellar wind microlensing of a faint background source

Abstract

By assuming the inverse square law of solar wind plasma density as representative of other stars, it is shown that just outside a star the {\it outward} deflection of a passing radio signal at $\nu \approx 1$~GHz (which is capable of penetrating the plasma) is about 5 times larger than the gravitational inward deflection by the star, and the ensuing lens equation which takes both effects into account is a cubic polynomial with three roots and a new strong lensing caustic. The geometric optics approach is valid for a radio source size $\lesssim 1$~pc. Microlensing magnification of a steady background source occurs typically over a timescale of milliseconds, resulting in $\approx 80$ Fast Radio Bursts (FRBs) per day over the whole sky, which can only perturb the isotropy of FRB distribution at the several \% level. Moreover, repeating FRBs could be triggered by the periodic interception of the line-of-sight of the background source by members of a binary system. The temporal signatures of such FRBs are consistent with the power spectrum of solar wind density fluctuations on corresponding scales, except the mean density of the wind is a few times higher than the solar value.

9 pages, 3 figures, ApJ in press

References in corpus (7)

• The Physics of Fast Radio Bursts
• Progress in Measurements of the Gravitational Bending of Radio Waves Using the VLBA
• Density Fluctuation Spectrum of Solar Wind Turbulence between Ion and Electron Scales
• The discovery and significance of fast radio bursts
• The effects of plasma on the magnification and time delay of strongly lensed fast radio bursts
• Gravitational lensing in the presence of plasma scattering with application to Fast Radio Bursts
• Detecting dark objects with plasma microlensing by their gravitational wakes