New constraint on cosmological variation of the proton-to-electron mass
  ratio from Q0528-250
  Molecular hydrogen transitions in quasar spectra can be used to constrain
variation in the proton-to-electron mass ratio, $\mu\equiv m_p/m_e$, at high
redshifts ($z\gtrsim 2$). We present here an analysis of a new spectrum of the
quasar Q0528$-$250, obtained on VLT/UVES (the Ultraviolet and Visual Echelle
Spectrograph, on the Very Large Telescope), and analyse the well-known H$_2$
absorber at $z=2.811$ in this spectrum. For the first time we detect HD
(deuterated molecular hydrogen) in this system with a column density of
$\log_{10}(N/\mathrm{cm^{-2}})=13.27 \pm 0.07$; HD is sensitive to variation in
$\mu$, and so we include it in our analysis. Using 76 H$_2$ and 7 HD
transitions we constrain variation in $\mu$ from the current laboratory value
to be $\Delta\mu/\mu = (0.3\pm 3.2_\mathrm{stat} \pm 1.9_\mathrm{sys})\times
10^{-6}$, which is consistent with no cosmological variation in $\mu$, as well
as with previous results from other H$_2$/HD absorbers. The main sources of
systematic uncertainty relate to accurate wavelength calibration of the spectra
and the re-dispersion of multiple telescope exposures onto the one pixel grid.
