The NH2D/NH3 ratio toward pre-protostellar cores around the UCH II region in IRAS 20293+3952

Context. The deuterium fractionation, D-frac, has been proposed as an evolutionary indicator in pre-protostellar and protostellar cores of low-mass star- forming regions. Aims. We investigate D-frac, with high angular resolution, in the cluster environment surrounding the UCH II region IRAS 20293+3952. Methods. We performed high angular resolution observations with the IRAM Plateau de Bure Interferometer (PdBI) of the ortho-NH(2)D1(11)-1(01) line at 85.926 GHz and compared them with previously reported VLA NH3 data. Results. We detected strong NH2D emission toward the pre-protostellar cores identified in NH3 and dust emission, all located in the vicinity of the UCH II region IRAS 20293+3952. We found high values of D-frac similar or equal to 0.1-0.8 in all the pre-protostellar cores and low values, D-frac < 0.1, associated with young stellar objects. Conclusions. The high values of D-frac in pre-protostellar cores could be indicative of evolution, although outflow interactions and UV radiation could also play a role.