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In the context of the ASAI (Astrochemical Surveys At IRAM) project, wecarried out an unbiased spectral survey in the millimeter window towards thewell known low-mass Class I source SVS13-A. The high sensitivity reached (3-12mK) allowed us to detect at least 6 HDO broad (FWHM ~ 4-5 km/s) emission lineswith upper level energies up to Eu = 837 K. A non-LTE LVG analysis implies thepresence of very hot (150-260 K) and dense (> 3 10^7 cm-3) gas inside a smallradius ($\sim$ 25 AU) around the star, supporting, for the first time, theoccurrence of a hot corino around a Class I protostar.  The temperature is higher than expected for water molecules are sublimatedfrom the icy dust mantles (~ 100 K). Although we cannot exclude we are observigthe effects of shocks and/or winds at such small scales, this could imply thatthe observed HDO emission is tracing the water abundance jump expected attemperatures ~ 220-250 K, when the activation barrier of the gas phasereactions leading to the formation of water can be overcome. We derive X(HDO) ~3 10-6, and a H2O deuteration > 1.5 10-2, suggesting that water deuterationdoes not decrease as the protostar evolves from the Class 0 to the Class Istage.

Hot and dense water in the inner 25 AU of SVS13-A