Most precise single redshift bound to $\mathsf{\Delta\alpha/\alpha}$

Abstract

Aims. Verification the theoretical prediction of oscillation of the fine-structure constant (e 2 / c) over cosmic time requires high precision / measurements at individual redshifts. In earlier studies the mean / values averaged over wide redshift intervals were usually reported. This requirement can be met using the single ion differential measurement (SIDAM) procedure. We apply SIDAM to the Fe ii lines associated with the damped Ly system observed at z abs = 1.15 in the spectrum of HE 0515-4414. Methods. The spectrum was obtained by means of the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT).