Gamma rays and X-rays from classical novae

The thermonuclear runaways occurring in accreted hydrogen shells on white dwarfs in close binary systems, that define the outbursts of the classical novae, provide an environment in which explosive hydrogen burning can produce significant concentrations of the interesting longer lived radioactive isotopes ⁷ Be (τ _1/2 =53.28 days), ²² Na,( τ _1/2 =2.605 years), and ²⁶ Al (τ _1/2 =7.2×10 ⁵ years), as well as of the short-lived positron-unstable isotopes ¹³ N, ¹⁴ O, ¹⁵ O, ¹⁷ F, and ¹⁸ F. It follows that nearby novae may produce flux levels of gamma rays, during several phases of their evolution, that are detectible with the Compton Gamma Ray Observatory. We briefly review the theoretical and observational picture with regard to the identified potential sources of gamma rays from novae. In particular, we reexamine the current situation regarding the production of ⁷ Be, ²² Na, and ²⁶ Al in nova outbursts, and provide updated estimates of the expected fluxes of ⁷ Be and ²² Na gamma rays from individual nova events. Expectations for X-rays from novae are also noted.