A new intermediate-mass protostar in the cepheus a HW2 region

We present the discovery of the first molecular hot core associated with an intermediate-mass protostar in the Cep A HW2 region. The hot condensation was detected from single-dish and interferometric observations of several high-excitation rotational lines ( from 100 to 880 K above the ground state) of SO 2 in the ground vibrational state and of HC3N in the vibrationally excited states v(7) = 1 and v(7) = 2. The kinetic temperature derived from v v both molecules is similar to 160 K. The high angular resolution observations (1.25 x 0.99) of the SO2 J = 28(7,21) -> 29(6,24) line ( 488 K above the ground state) show that the hot gas is concentrated in a compact condensation with a size of similar to 0.6 (similar to 430 AU), located 0.4 ( 300 AU) east from the radio jet HW2. The total SO 2 column density in the hot condensation is similar to 10(18) cm(-2), with an H-2 column density ranging from similar to 10(23) to 6 x 10(24) cm(-2). The H-2 density and the SO2 fractional abundance must be larger than 10(7) cm(-3) and 2 x 10(-7), respectively. The most likely alternatives for the nature of the hot and very dense condensation are discussed. From the large column densities of hot gas, the detection of the HC3N vibrationally excited lines, and the large SO 2 abundance, we favor the interpretation of a hot core heated by an intermediate-mass protostar of 103 L,. This indicates that the Cep A HW2 region contains a cluster of very young stars.