2001ApJ...552L.163L

We report the detection of the doubly deuterated forms of ammonia (ND₂H) and formaldehyde (D₂CO) toward 16293E, a newly identified low-luminosity protostar in the ρ Ophiucus molecular complex. The abundances of ND₂H and D₂CO compared with their hydrogenated counterparts NH₃ and H₂CO are ∼3% and 40%±20%, respectively. To date, 16293E is thus the source with the highest levels of multiple deuteration: [ND₂H]/[NH₃] is 5-6 times larger there than in the only other astronomical source where ND₂H has ever been found, the dense ammonia core of L134N; and [D₂CO]/[H₂CO] is more than 5 times higher than in the proto-binary system IRAS 16293-2422. The relative abundances of doubly deuterated molecules in low-luminosity protostars are much higher than their current gas-phase [D]/[H] ratios would suggest and, therefore, likely reflect active grain surface chemistry followed by some desorption process.