Novae II. Model, multi-band outburst, bipolar ejecta, accretion disk, relativistic electrons, etc

Abstract

The study of novae is continued and a self-consistent updated physical model for classical/recurrent novae derived from multi-wavelength observations is presented. In particular, observations of novae support the origin of the optical continuous emission in the outburst ejecta, mass-based segregation and clump formation in the ejecta, origin of the Orion, diffuse enhanced lines and dust in the clumps, prompt Fe II line formation in swept-up material, energising of electrons to relativistic velocities by the explosion and the existence of a large cool envelope around the accreting white dwarf in quiescence. The rapid transfer of thermonuclear energy should be adiabatic which energises and ejects all the particles in the overlying layers. Our study results in the following conclusions which are relevant for novae and other astrophysical systems: (1) Electrons are instantaneously energised to relativistic velocities in the explosion alongside the heavier atoms and ions. No post-ejection shock acceleration needs to be invoked. (2) Rotation of an incompressible spherical accreting object leads to a latitude-dependent potential such that the accretion rate is maximum at the poles and minimum at the equator. This will form a prolate-shaped envelope. Energetic expulsion of this envelope will result in a bipolar ejecta/outflow. Such outflows cannot be ejected from non-rotating spherical objects. (3) The latitude-dependent accretion rates in a rotating accreting object will also lead to accumulation of the infalling matter outside the object in the non-polar regions thus forming an accretion disk. The angular momentum of the incoming matter plays no role in the formation of an accretion disk. Accretion disks cannot form around a non-rotating object.