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Astron. Astrophys. 319, 909-922 (1997)

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The contribution of O-Ne-Mg novae to the 26Al production in the Galaxy

U. Kolb 1, 2, 3 and M. Politano 4

1 Astronomy Group, University of Leicester, Leicester, LE1 7RH, UK (uck@star.le.ac.uk)
2 UCO/Lick Observatory, Board of Studies in Astronomy and Astrophysics, UCSC, Santa Cruz, CA 95064, USA
3 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany
4 Dept. of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA (politano@phyast.la.asu.edu)

Received 15 March 1996 / Accepted 19 July 1996

Abstract

Recent COMPTEL observations revealed inhomogeneities in the spatial distribution of the Galactic 26 Al 1.809 MeV [FORMULA] -ray emission, which reduces the required amount of 26 Al in a homogeneous background from [FORMULA] (the value assuming all of the radiation is from a homogeneous background) to [FORMULA]. Using recent nova population models and simulations of classical nova outbursts we reinvestigate the question of whether nova outbursts on oxygen-neon-magnesium white dwarfs (ONeMg WDs) contribute significantly to the production of 26 Al in the Galaxy. We find an upper limit of [FORMULA] for the amount of 26 Al produced by ONeMg novae in the Galaxy, if we adopt a value of 30% for the fraction [FORMULA] of novae in our models that are ONeMg novae and choose optimal models and parameter values. Uncertainties in both observations and theory do not allow us to quote a lower limit with any confidence at this time. Choosing models and parameter values that are more consistent with independent observational quantities gives an 26 Al production of [FORMULA], again for an assumed [FORMULA] of 30%. However, this value is dependent on our assumption of choosing the same amount of mixing between the underlying WD material and the accreted companion material for the entire population. If the mean amount of mixing in ONeMg novae is [FORMULA] a factor of 2 higher than the mean maximum amount of mixing for all novae, then we estimate that ONeMg novae can produce a sufficient amount of 26 Al [FORMULA] to account for the entire diffuse background emission observed by COMPTEL. We explore to what extent ejecta abundances in well-studied novae support this possibility.

Key words: novae, cataclysmic variables – stars: evolution – stars: white dwarfs – gamma-rays: theory – nuclear reactions, nucleosynthesis, abundances

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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