Testing For Azimuthal Abundance Gradients In M101
  New optical spectra of 28 H II regions in the M101 disk have been obtained,
yielding 10 new detections of the [O III]{\lambda}4363 auroral line. The oxygen
abundance gradient measured from these data, combined with previous
observations, displays a local scatter of 0.15+/-0.03 dex along an arc in the
west side of the galaxy, compared with a smaller scatter of 0.08+/-0.01 dex in
the rest of the disk. One of the H I I regions in our sample (H27) has a
significantly lower oxygen abundance than surrounding nebulae at a similar
galactocentric distance, while an additional, relatively nearby one (H128) was
already known to have a high oxygen abundance for its position in the galaxy.
These results represent marginal evidence for the existence of moderate
deviations from chemical abundance homogeneity in the interstellar medium of
M101. Using a variety of strong-line abundance indicators, we find no evidence
for significant large-scale azimuthal variations of the oxygen abundance across
the whole disk of the galaxy.
