Updated constraints on spatial variations of the fine-structure constant
  Recent work by Webb {\it et al.} has provided indications of spatial
variations of the fine-structure constant, $\alpha$, at a level of a few parts
per million. Using a dataset of 293 archival measurements, they further show
that a dipole provides a statistically good fit to the data, a result
subsequently confirmed by other authors. Here we show that a more recent
dataset of dedicated measurements further constrains these variations: although
there are only 10 such measurements, their uncertainties are considerably
smaller. We find that a dipolar variation is still a good fit to the combined
dataset, but the amplitude of such a dipole must be somewhat smaller:
$8.1\pm1.7$ ppm for the full dataset, versus $9.4\pm2.2$ ppm for the Webb {\it
et al.} data alone, both at the $68.3\%$ confidence level. Constraints on the
direction on the sky of such a dipole are also significantly improved. On the
other hand the data can't yet discriminate between a pure spatial dipole and
one with an additional redshift dependence.
