SIMBAD references

We present ground-based 2.1 to 4.2µm observations of four low-mass protostars. We searched for the 4.1µm OD stretch band, characteristic of solid HDO in grain mantles. We did not detect solid HDO in any of the four sources, but we derive 3σ upper limits from 0.5% to 2% for the HDO/H₂O ratio depending on the source. These ratios provide strong constraints to solid-state deuteration models when compared to deuterium fractionation values observed in the gas phase. We discuss various scenarios that could lead to such a low water deuteration compared to the high formaldehyde and methanol deuteration observed in the gas-phase.