A Survey for Hydroxyl in the THOR Pilot Region around W43
  We report on observations of the hydroxyl radical (OH) within The H{\sc I},
OH Recombination line survey (THOR) pilot region. The region is bounded
approximately between Galactic coordinates l=29.2 to 31.5$^\circ$ and b=-1.0 to
+1.0$^\circ$ and includes the high-mass star forming region W43. We identify
103 maser sites, including 72 with 1612\,MHz masers, 42 showing masers in
either of the main line transitions at 1665 and 1667\,MHz and four showing
1720\,MHz masers. Most maser sites with either main-line or 1720\,MHz emission
are associated with star formation, whereas most of the 1612\,MHz masers are
associated with evolved stars. We find that nearly all of the main-line maser
sites are co-spatial with an infrared source, detected by GLIMPSE. We also find
diffuse OH emission, as well as OH in absorption towards selected unresolved or
partially resolved sites. Extended OH absorption is found towards the well
known star forming complex W43 Main.
