A New Intermediate-Mass Protostar in the Cepheus A HW2 Region

We present the discovery of the first molecular hot core associated with anintermediate mass protostar in the CepA HW2 region. The hot condensation wasdetected from single dish and interferometric observations of several highexcitation rotational lines (from 100 to 880K above the ground state) of SO2 inthe ground vibrational state and of HC3N in the vibrationally excited statesv7=1 and v7=2. The kinetic temperature derived from both molecules is 160K. Thehigh-angular resolution observations (1.25'' x 0.99'') of the SO2J=28(7,21)-29(6,24) line (488K above the ground state) show that the hot gas isconcentrated in a compact condensation with a size of 0.6''(430AU), located0.4'' (300AU) east from the radio-jet HW2. The total SO2 column density in thehot condensation is 10E18cm-2, with a H2 column density ranging from 10E23 to 6x 10E24cm-2. The H2 density and the SO2 fractional abundance must be largerthan 10E7cm-3 and 2 x 10E-7 respectively. The most likely alternatives for thenature of the hot and very dense condensation are discussed. From the largecolumn densities of hot gas, the detection of the HC3N vibrationally excitedlines and the large SO2 abundance, we favor the interpretation of a hot coreheated by an intermediate mass protostar of 10E3 Lo. This indicates that theCepA HW2 region contains a cluster of very young stars