Revision of VLT/UVES constraints on a varying fine-structure constant

We critically review the current null results on a varying fine-structure constant, alpha, derived from Very Large Telescope (VLT)/Ultraviolet and Visual Echelle Spectrograph (UVES) quasar absorption spectra, focusing primarily on the many-multiplet analysis of 23 absorbers from which Chand et al. reported a weighted mean relative variation of Delta alpha/alpha = (-0.06 +/- 0.06) x 10(-5). Our analysis of the same reduced data, using the same fits to the absorption profiles, yields very different individual Delta alpha/alpha values with uncertainties typically larger by a factor of similar to 3. We attribute the discrepancies to flawed parameter estimation techniques in the original analysis and demonstrate that the original Delta alpha/alpha values were strongly biased towards zero. Were those flaws not present, the input data and spectra should have given a weighted mean of Delta alpha/alpha = (-0.44 +/- 0.16) x 10(-5). Although this new value does reflect the input spectra and fits (unchanged from the original work - only our analysis is different), we do not claim that it supports previous Keck/High Resolution Echelle Spectrograph (HIRES) evidence for a varying alpha: there remains significant scatter in the individual Delta alpha/alpha values which may stem from the overly simplistic profile fits in the original work. Allowing for such additional, unknown random errors by increasing the uncertainties on Delta alpha/alpha to match the scatter provides a more conservative weighted mean, Delta alpha/alpha = (-0.64 +/- 0.36) x 10(-5). We highlight similar problems in other current UVES constraints on varying alpha and argue that comparison with previous Keck/HIRES results is premature.