Amanda Weltman tells us about fast radio bursts (FRBs), which have been in the news recently in the context of the “missing baryons”. She tells us about that measurement (and her own theoretical work preceding it), but also about FRBs in general and how they’ll be useful for cosmology.

FRBs are what it sounds like they are, short bursts of radio frequency radiation detected from outside the solar system. We still don’t know 100% what their origin is, but it is possible at least some of them come from magnetars (neutron stars with very large magnetic fields).

A very useful property of FRBs is that they have a non-zero dispersion relation in the intergalactic medium, because they interact with the ionised electrons in that space. This makes it possible to measure the electron density of the inter-galactic medium, and/or to measure how far the FRBs are away from us. In each case this is based on how much the frequencies within each FRB have dispersed by the time we detect them.

FRB theory wiki: https://frbtheorycat.org/index.php/Main_Page
Amanda: https://en.wikipedia.org/wiki/Amanda_Weltman

Relevant papers:
Probing Diffuse Gas with Fast Radio Bursts https://arxiv.org/abs/1909.02821
Fast Radio Burst Cosmology and HIRAX https://arxiv.org/abs/1905.07132
A Living Theory Catalogue for FRBs https://arxiv.org/abs/1810.05836