We present the results of formaldehyde and methanol deuteration measurements towards the Class I low-mass protostar SVS13-A , in the framework of the IRAM 30-m ASAI ( Astrochemical Surveys At IRAM ) project .
We detected emission lines of formaldehyde , methanol , and their deuterated forms ( HDCO , D _ { 2 } CO , CHD _ { 2 } OH , CH _ { 3 } OD ) with E _ { up } up to 276 K. The formaldehyde analysis indicates T _ { kin } \sim 15 – 30 K , n _ { H _ { 2 } } \geq 10 ^ { 6 } cm ^ { -3 } , and a size of about 1200 AU suggesting an origin in the protostellar envelope .
For methanol we find two components : ( i ) a high temperature ( T _ { kin } \sim 80 K ) and very dense ( > 10 ^ { 8 } cm ^ { -3 } ) gas from a hot corino ( radius \simeq 35 AU ) , and ( ii ) a colder ( T _ { kin } \leq 70 K ) and more extended ( radius \simeq 350 AU ) region .

The deuterium fractionation is 9 \times 10 ^ { -2 } for HDCO , 4 \times 10 ^ { -3 } for D _ { 2 } CO , and 2 – 7 \times 10 ^ { -3 } for CH _ { 2 } DOH , up to two orders of magnitude lower than the values measured in Class 0 sources .
We derive also formaldehyde deuteration in the outflow : 4 \times 10 ^ { -3 } , in agreement with what found in the L1157–B1 protostellar shock .
Finally , we estimate [ CH _ { 2 } DOH ] / [ CH _ { 3 } OD ] \simeq 2 .
The decrease of deuteration in the Class I source SVS13-A with respect to Class 0 sources can be explained by gas-phase processes .
Alternatively , a lower deuteration could be the effect of a gradual collapse of less deuterated external shells of the protostellar evelope .
The present measurements fill in the gap between prestellar cores and protoplanetary disks in the context of organics deuteration measurements .