An implicit hydrodynamic code following the explosion of classical novae , from the accretion phase up to the final ejection of the envelope , has been coupled to a Monte-Carlo code able to simulate their gamma-ray emission .
Carbon-oxygen ( CO ) and oxygen-neon ( ONe ) novae have been studied and their gamma-ray spectra have been obtained , as well as the gamma-ray light curves for the important lines ( e ^ { - } –e ^ { + } annihilation line at 511 keV , ^ { 7 } Be decay-line at 478 keV and ^ { 22 } Na decay-line at 1275 keV ) .
The detectability of the emission by CGRO instruments has been analyzed .
It is worth noticing that the \gamma -ray signature of a CO nova is different from that of an ONe one .
In the CO case , the 478 keV line is very important , but lasts only for \sim 2 months .
In the ONe case , the 1275 keV line is the dominant one , lasting for \sim 4 years .
In both cases , the 511 keV line is the most intense line at the beginning , but its short duration ( \sim 2 days ) makes it very difficult to be detected .
It is shown that the negative results from the observations made by COMPTEL up to now are consistent with the theoretical predictions .
Predictions of the future detectability by the INTEGRAL mission are also made .