HCN/HNC chemistry in shocks: a study of L1157-B1 with ASAI

HCN and its isomer HNC play an important role in molecular cloud chemistry the formation of more complex molecules. We investigate here impact protostellar shocks on abundances from high-sensitivity IRAM 30m observations prototypical shock region L1157-B1 envelope associated Class 0 protostar, as a proxy for pre-shock gas. The isotopologues H$^{12}$CN, HN$^{12}$C, H$^{13}$CN, HN$^{13}$C, HC$^{15}$N, H$^{15}$NC, DCN DNC were all detected towards both regions. Abundances excitation conditions obtained radiative transfer analysis line emission under assumption Local Thermodynamical Equilibrium. In gas, are similar to those encountered dark clouds, with HCN/HNC abundance ratio $\approx 1$ isotopologues. A strong D-enrichment (D/H$\approx 0.06$) is measured There no evidence $^{15}$N fractionation neither quiescent nor shocked At passage shock, increase gas phase different manners so that relative increases by factor 20. gas-grain chemical model UCLCHEM allows us reproduce observed trends C-type density $n$(H)= $10^5$cm$^{-3}$ velocity $V_s= 40$km/s. conclude variations across mainly caused sputtering grain mantle material relation history ices.