Probing the variability of the fine-structure constant with the VLT/UVES

We assess the cosmological variability of the fine-structure constant α from the analysis of an ensemble of , , , , , and absorption lines at the redshift toward the QSO HE 0515–4414 by means of the standard many-multiplet (MM) technique and its revision based on linear regression (RMM). This is the first time the MM technique is applied to exceptional high-resolution and high signal-to-noise QSO spectra recorded with the UV-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT). Our analysis results in and , which are the most stringent bounds hitherto infered from an individual QSO absorption system. Our results support the null hypothesis at a significance level of 91 percent, whereas the support for the result presented in former MM studies is 12 percent.