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Classical novae are considered to be the major source of the ISM enrichment with the isotopes of [sup 13]C, [sup 15]N, and [sup 22]Na. The latter, radioactive [sup 22]Na, 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 [sup 22]Na from the frequent novae in the bulge will lead to an observable extended emission. Additionally, a [sup 22]Na detection from the single nova can be used to verify predictions of the modem 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 [sup 22]Na; and (2) — we pursued the [sup 22]Na 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 [sup 22]Na 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. [ABSTRACT FROM AUTHOR]

The evolution of the γ-ray emission from GRO J0422+32 after its main outburst of August 1992 was followed by COMPTEL during 25 observation periods (VPs) between August 1992 and August 1997, where NPer 92 was in the FoV of COMPTEL, and for 3 VPs preceding the nova outburst. It is found that the NPer 92 γ-ray emission is greatly confined to energies between 1.5 and 2.0 MeV. This emission is prominent during observations that correspond to phases between 0.0 and 0.5 of the ~ 120 days period discovered in the nova optical emission. This periodical activity of the nova in form of mini-outbursts is supported by the detection of the γ-ray emission from GRO J0422+32 in seven episodes up to ~ 1800 days (August 1997) after the main outburst, and by the All Sky Monitor's (ASM, Rossi XTE) detection of X-ray mini-outbursts (four episodes). In one episode we have succeeded to derive a contemporaneous spectrum based on the measurements by COMPTEL, ASM and BATSE. The plausible mechanisms of the GRO J0422+32 periodical mini-outbursts and of its characteristic γ-ray emission are discussed. The possibility of the system being a triple is also evaluated. [ABSTRACT FROM AUTHOR]

The COMPTEL telescope on board the Compton Gamma-Ray Observatory (CGRO) is capable of imaging γ-ray line sources, like classical novae, in the MeV regime at a level of sensitivity up to a few 10[SUP-5] photons cm[SUP-2]s[SUP-1]. At this level of sensitivity quite high expectations can be placed on the detection of the predicted [SUP22]Na γ-ray line at 1.275 MeV from nearby novae. Unfortunately, no positive detection of the nova-produced [SUP22]Na was reported until recently. We have used COMPTEL data collected up to the 2nd CGRO reboost to assess (1) - sodium production by individual novae, and (2) - the Galactic distribution of the nova-produced [SUP22]Na. [ABSTRACT FROM AUTHOR]

The COMPTEL telescope on board the Compton Gamma-Ray Observatory (CGRO) is capable of imaging γ-ray line sources, like classical novae, in the MeV regime at a level of sensitivity up to a few 10[sup -5] photons cm[sup -2] s[sup -1]. At this level of sensitivity quite high expectations can be placed on the detection of the predicted [sup 22]Na γ-ray line at 1.275 MeV from nearby novae. We have used COMPTEL data collected up to the 2[sup nd] CGRO reboost to update previously published limits for the sodium production by novae. Results of the [sup 22]Na line emission studies from the old and the most recent novae are discussed and compared with model predictions. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

[sup 44]Ti is one of the few radioactive nuclei produced abundantly in supernovae (SNe). Because its life time is comparable to the typical time between supernovae in the Galaxy, γ-ray lines from [sup 44]Ti provide a powerful tool for the search for optically obscured supernovae that occurred during the last few 100 years. We present our analysis of COMPTEL data (Cycle 1–6), comparing γ-ray line images and flux distributions with Monte Carlo simulations of SNe in the Galaxy. Assuming standard SNe distribution models and theoretical estimates of the [sup 44]Ti yields, we constrain the Galactic supernova rate. We compare these constraints with those obtained from the historical record covering the last millennium. Relating the current supernova rate to the observed [sup 44]Ti solar abundance through chemical evolution models, agreement can be obtained only if there is a special type of supernova (e.g., helium detonations) that produces large amounts of [sup 44]Ti, but with a very low event rate. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]