Fast Radio Bursts
Fast Radio Bursts (FRBs) are a recently discovered radio transient of ~ 10–3 s duration. Radio observations give the dispersion measure (DM) of the bursting objects, the integrated electron density along their line of sight. At this point, it is known that they are extragalactic in origin, and a precise optical red shift is available for the one repeating FRB, though the discovery rate indicates that they are very common in our universe. Current theories suggest they come from a unique type of coherent emission from a highly magnetized neutron star. Because each burst will yield a DM, combining this with optical red shift and spectroscopic absorption information gives independent information on distances, and the matter and ionization distribution along the line of sight, and therefore the ionization history of the universe. This, in turn, has implications for the history of the first stars, quasars, and other sources of ionizing emission, and the imprints of these objects and processes on the cosmic mm-microwave background (CMB). We therefore propose a project, summarized in the table below, to use these objects to advance our knowledge of the universe by 1) developing a theory of the origin of FRBs, 2) exploiting their use as cosmological, astrophysical, and fundamental physics probes, and 3) planning the observations and instrumentation for these probes.
Optical/ IR Detection of FRBs – An Exciting, Challenging Prospect
Observations of optical-IR (OIR) flashes, especially if they are identified with a coincident radio signal, provide powerful information on the radiation mechanism and the physics of the source, including new information about compact objects and likely high magnetic fields. The precise location that comes with OIR imaging allows determination of the critical redshift to be measured with follow-up (non-timely) OIR observations. As of this writing, Sept. 1 2017, there are dozens of FRB events known, but only one repeating FRB. A known repeating source allows optical-quality position determination by multi-antenna radio observations, but no such capability is available for the non-repeaters. There are already modest limits to the optical emission from the repeater (Hardy et al., 2017, arXiv:1708.06156), but with conventional instrumentation. Theoretical models predict that in a ~ 20 µs flash (the radio flash has a longer duration due to dispersion), ~ 102 photons/m2 might be produced in a standard astronomical R band, with a spectrum that is quite red, that is, drops steeply with increasing frequency (Kumar et al. 2017). Detecting such emission is a multi-dimensional challenge, but one that the ECL is uniquely suited to take up.