  We report the detection of complex molecules (HCOOCH_3, HCOOH and CH_3CN),
signposts of a "hot core" like region, toward the low mass, Class 0 source
NGC1333-IRAS4A. This is the second low mass protostar where such complex
molecules have been searched for and reported, the other source being
IRAS16293-2422. It is therefore likely that compact (few tens of AUs) regions
of dense and warm gas, where the chemistry is dominated by the evaporation of
grain mantles, and where complex molecules are found, are common in low mass
Class 0 sources.Given that the chemical formation timescale is much shorter
than the gas hot core crossing time, it is not clear whether the reported
complex molecules are formed on the grain surfaces (first generation molecules)
or in the warm gas by reactions involving the evaporated mantle constituents
(second generation molecules). We do not find evidence for large differences in
the molecular abundances, normalized to the formaldehyde abundance, between the
two solar type protostars, suggesting perhaps a common origin.

Astrophysics