Discovery of New Interacting Supernova Remnants in the Inner Galaxy

OH(1720 MHz) masers are excellent signposts of interaction between supernova remnants (SNRs) and molecular clouds. Using the Green Bank Telescope and Very Large Array we have surveyed 75 SNRs and six candidates for masers. Four SNRs are detected with OH masers: G5.4-1.2, G5.7-0.0, G8.7-0.1, and G9.7-0.0. Two SNRs, G5.7-0.0 and G8.7-0.1, have TeV γ-ray counterparts which may indicate a local cosmic ray enhancement. It has been noted that maser-emitting (ME) SNRs are preferentially distributed in the molecular ring and nuclear disk. We use the present and existing surveys to demonstrate that masers are strongly confined to within |l| <= 50° at a rate of 15% of the total SNR population. All new detections are within 10° Galactic longitude emphasizing this trend. Additionally, a substantial number of SNR masers have peak fluxes at or below the detection threshold of existing surveys. This calls into question whether maser surveys of Galactic SNRs can be considered complete and how many ME remnants remain to be detected in the Galaxy.