The heating of nova ejecta by radioactive decays of the β-unstable nuclei

Shlomi Pistinner, Giora Shaviv, Sumner Starrfield

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Recent nucleosynthesis and hydrodynamic calculations of the consequences of accretion onto massive ONeMg white dwarf stars show that under certain circumstances significant amounts of the β-unstable nuclei can be produced and ejected by the resulting explosion. We use these calculations as a guide in order to obtain the conditions under which the heating of the ejected material by the nonthermal electrons and positrons produced by the decays of the β-unstable nuclei is sufficient to overcome the cooling from adiabatic expansion and lead to the production of X-ray-emitting coronal gas. These conditions are as follows: 1. A mass fraction for 22Na of the order of 10-3 or greater. 2. An expansion velocity in the range ∼ 102-103 km s-1. 3. A photospheric radius of ∼ 1014 cm. 4. If the density distribution in the atmosphere satisfies a power law, then the exponent must be less than 3 for heating to overcome adiabatic cooling. Both the simulations of the outburst and the model atmosphere fits to the observed energy distributions, however, imply that the exponent is ≥ 3 during the early phases of the outburst. Nevertheless, for a value of the exponent of 2, we predict the time when hot coronal gas can form during the expansion phases of the envelope.

Original languageEnglish (US)
Pages (from-to)794-801
Number of pages8
JournalAstrophysical Journal
Volume437
Issue number2
StatePublished - Dec 20 1994

Keywords

  • Novae, cataclysmic variables
  • Nuclear reactions, nucleosynthesis, abundances
  • Stars: coronae
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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