2019MNRAS.488.1908H

Nature of dark energy remains unknown. Especially, to constrain the time variability of the dark energy, a new, standardizable candle that can reach more distant Universe has been awaited. Here we propose a new distance measure using fast radio bursts (FRBs), which are a new emerging population of ∼ ms time-scale radio bursts that can reach high-z in quantity. We show an empirical positive correlation between the time-integrated luminosity (L_ν) and rest-frame intrinsic duration (w_int, rest_) of FRBs. The L_ν-w_int, rest_ correlation is with a weak strength but statistically very significant, i.e. Pearson coefficient is ∼ 0.5 with P value of ∼0.038, despite the smallness of the current sample. This correlation can be used to measure intrinsic luminosity of FRBs from the observed w_int, rest_. By comparing the luminosity with observed flux, we measure luminosity distances to FRBs, and thereby construct the Hubble diagram. This FRB cosmology with the L_ν-w_int, rest_ relation has several advantages over SNe Ia, Gamma-Ray Burst (GRB), and well-known FRB dispersion measure (DM)-z cosmology; (i) access to higher redshift Universe beyond the SNe Ia, (ii) high event rate that is ∼3 orders of magnitude more frequent than GRBs, and (iii) it is free from the uncertainty from intergalactic electron density models, i.e. we can remove the largest uncertainty in the well-debated DM-z cosmology of FRB. Our simulation suggests that the L_ν-w_int, rest_ relation provides us with useful constraints on the time variability of the dark energy when the next-generation radio telescopes start to find FRBs in quantity.