Models for the soft X-ray emission of post-outburst classical novae

A hydrostatic and stationary white dwarf envelope model has been developed for the study of the post-outburst phases of classical novae and their soft X-ray emission. Several white dwarf masses and chemical compositions typical for classical novae have been considered. The results show that the luminosity, maximum effective temperature and envelope masses depend on the white dwarf mass and on the chemical composition. Envelope masses for which equilibrium solutions exist are pretty small ~10^{-7}-10^{-6} Msun, thus leading to a short duration of the soft X-ray emitting phase of classical novae, in agreement with most of the observations. The models presented provide a useful tool for the determination of the white dwarf properties from observable parameters in the X-ray range.Comment: 15 pages, 11 figures, 2 tables, accepted for publication in Astronomy & Astrophysic

Thermonuclear Runaways on Accreting White Dwarfs: Models of Classical Novae Explosions

The mechanism of classical novae explosions is explained, together with some of their observational properties. The scarce but not null impact of novae in the chemical evolution of the Milky Way is analyzed, as well as their relevance for the radioactivity in the Galaxy. A special emphasis is given to the predicted gamma-ray emission from novae and its relationship with the thermonuclear model itself and its related nucleosynthesis.Comment: 10 pages, 2 figures, LaTex (aipproc.sty), review to appear in "Cosmic Explosions", proceedings. of the 10th Annual October Maryland Astrophysics Conference, eds. S. Holt and W. W. Zhang, AI

Evidence for Nonlinear Diffusive Shock Acceleration of Cosmic Rays in the 2006 Outburst of RS Ophiuchi

Spectroscopic observations of the 2006 outburst of RS Oph at both infrared (IR) and X-ray wavelengths have shown that the blast wave has decelerated at a higher rate than predicted by the standard test-particle adiabatic shock-wave model. The observed blast-wave evolution can be explained, however, by the diffusive shock acceleration of particles at the forward shock and the subsequent escape of the highest energy ions from the acceleration region. Nonlinear particle acceleration can also account for the difference of shock velocities deduced from the IR and X-ray data. We discuss the evolution of the nova remnant in the light of efficient particle acceleration at the blast wave.Comment: 4 pages, 2 figures. To appear in "RS Ophiuchi (2006) and the recurrent nova phenomenon", eds. A. Evans, M.F. Bode & T.J. O'Brien, ASP Conf. Se

Nuclear uncertainties in the NeNa-MgAl cycles and synthesis of 22Na and 26Al in classical novae

Classical novae eject significant amounts of matter into the interstellar medium, as a result of thermonuclear runaways. Nucleosynthesis associated with nova outbursts includes products from explosive H burning, such as 17O, 15N and 13C, and also radioactive species like 7Be, 22Na and 26Al. In this paper we report on new hydrodynamic calculations of nova outbursts, from the onset of accretion to mass ejection. We stress the role played by the nuclear uncertainties associated with key reactions of the NeNa-MgAl cycles on the synthesis of 22Na and 26Al.Comment: 4 pages (to appear in "Nuclei in the Cosmos V" Conference Proceedings