### 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 ^{22}Na of the order of 10^{-3} or greater. 2. An expansion velocity in the range ∼ 10^{2}-10^{3} km s^{-1}. 3. A photospheric radius of ∼ 10^{14} 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 language | English (US) |
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Pages (from-to) | 794-801 |

Number of pages | 8 |

Journal | Astrophysical Journal |

Volume | 437 |

Issue number | 2 |

State | Published - 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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## Cite this

*Astrophysical Journal*,

*437*(2), 794-801.