The effects of new nuclear reaction rates and opacities on hydrodynamic simulations of the nova outburst

We report on the results of new calculations of thermonuclear runaways on 1.25 M_⊙ oxygen, neon, and magnesium white dwarfs, using our one-dimensional, fully implicit, hydrodynamic stellar evolution code that includes a large nuclear reaction network. We have updated the nuclear reaction network by including both new and improved experimental and theoretical determinations of the nuclear reaction rates. We have also incorporated the carbon-rich OPAL opacity tables. Our results show that the changes in the reaction rates and opacities that we have introduced produce important changes with respect to our previous studies. For example, a smaller amount of ²⁶Al is produced, while the abundances of ³¹P and ³²S increase by factors of more than 2. This change is attributed to the increased proton-capture reaction rates for some of the intermediate-mass nuclei near ²⁶Al and beyond, such that nuclear fusion to higher mass nuclei is enhanced. We also find that our predicted values for the amount of mass ejected in the outburst are at least a factor of 10 less than observed. The low values for the amount of ejected mass is a consequence of the fact that the OPAL opacities are larger than those we previously used, which results in more heat being trapped in the nuclear-burning regions and, therefore, less mass being accreted onto the white dwarf.