IR EMISSION OF THE SYMBIOTIC NOVA HM SAGI TTAE

The energy distribution in the spectrum of the symbiotic nova HM Sge i n the range 1 - 100 mum is shown to be formed by four principal IR sou rces: a cool component of HM Sge (a Mira-type star) and three main str uctural elements of the gas and dust envelope of this binary system. F irst, these three structural elements include a compact (< 10(15) cm) and hot part of the dust envelope, which concentrates around the Mira, changes its brightness and temperature (from 700 to 950 K) with a pul sation period of the Mira, and significantly [tau(J) = 0.9] attenuates emission from this variable. Second, these include a thin (DELTAR/R m uch-less-than 1, R greater-than-or-equal-to 10(15) cm) atmospheric gas and dust envelope formed after an outburst of the hot component in HM Sge as a result of the nearby material being swept up and raked up by its stellar wind. In the region between the stars, this envelope is h eated by emission from the hot component, both nonprocessed and proces sed by gas, to a temperature T = 750 K, and do not change its brightne ss on a time scale of a year. Third, these elements include the outer (greater-than-or-equal-to 10(16) cm) parts of the circumstellar envelo pe around HM Sge (and material raked up by the stellar wind of the hot component along the direction opposite to the direction to its cool c omponent), which are primarily heated by radiation from the hot subdwa rf to T = 200 K. In percentage terms, the contribution of the IR sourc es listed above to the total flux of HM Sge during maximum light of th e Mira is 22%, 25%, 31%, and 22%, respectively.