Global Galactic Distribution of Classical Novae

Abstract

Classical novae are considered to be the major source of the ISM enrichment with the isotopes of 13C, 15N, and 22Na. The latter, radioactive 22Na, that decays producing penetrating 1.275 MeV γ‐ray photon, could be very useful as a probe of the galactic global distribution of novae. It is expected that the accumulation of 22Na from the frequent novae in the bulge will lead to an observable extended emission. Additionally, a 22Na detection from the single nova can be used to verify predictions of the modern thermonuclear runaway theory (TNR) applied to classical novae. To gain a better insight into this problem we have used a two‐way approach. Namely: (1) ‐ we have studied the global galactic distribution of the 1.275 MeV γ‐ray line emission assuming that it is mostly originates from decay of the novae‐produced 22Na; and (2) ‐ we pursued the 22Na line emission detection from recent individual novae. The combination of both approaches makes possible to tap rather uncertain galactic novae rate by comparing observations of the individual Galactic novae with the integrated 22Na line emission from the disk and/or bulge population. The COMPTEL telescope on board the Compton Gamma‐Ray Observatory (CGRO), due to its combination of imaging and spectroscopic capabilities, is suitable to address the above ideas.