Shock Excited 1720 MHz Masers

Abstract

1720 MHz OH masers have been detected towards a number of supernova remnants (SNRs) at the shock interface where the SNR slams into the interstellar medium. Models indicate that these masers are shock excited and can only be produced under tight constraints of the physical conditions. In particular, the masers can only form behind a C-type shock. Jets from newlyformed stars plow into the surrounding gas, creating nebulous regions known as Herbig Haro (HH) objects. Signatures of C-type shocks have been found in many HH objects. If conditions behind the shock fronts of HH objects are able to support 1720 MHz OH masers they would be a usefull diagnostic tool for star formation. A survey toward HH objects detected a number of 1720 MHz OH lines in emission, but future observations with arrays are required to confirm the presence of masers.