Cyclic-C _ { 3 } HD ( c -C _ { 3 } HD ) is a singly deuterated isotopologue of c -C _ { 3 } H _ { 2 } , which is one of the most abundant and widespread molecules in our Galaxy .
We observed IRAS 16293-2422 in the 3 mm band with a single frequency setup using the EMIR heterodyne 3 mm receiver of the IRAM 30m telescope .
We observed seven lines of c -C _ { 3 } HD and three lines of c -C _ { 3 } H _ { 2 } .
Observed abundances are compared with astrochemical simulations using the NAUTILUS gas-grain chemical model .
Assuming that the size of the protostellar envelope is 3000 AU and same excitation temperatures for both c -C _ { 3 } H _ { 2 } and c -C _ { 3 } HD , we obtain a deuterium fraction of 14 _ { -3 } ^ { +4 } \% .