We present the results of GBT observations of all four ground-state hydroxyl ( OH ) transitions toward 15Â supernova remnants ( SNRs ) which show OH ( 1720 MHz ) maser emission .
This species of maser is well established as an excellent tracer of an ongoing interaction between the SNR and dense molecular material .
For the majority of these objects we detect significantly higher flux densities with a single dish than has been reported with interferometric observations .
We infer that spatially extended , low level maser emission is a common phenomenon that traces the large-scale interaction in maser-emitting SNRs .
Additionally we use a collisional pumping model to fit the physical conditions under which OH is excited behind the SNR shock front .
We find the observed OH gas associated with the SNR interaction having columns N _ { \mathrm { OH } } \leq 1.5 \times 10 ^ { 17 } cm ^ { -2 } , temperatures of 20–125 K , and densities \sim 10 ^ { 5 } cm ^ { -3 } .