1 Vilspa
2 Keele University
Classical nova eruptions occur as a result of thermonuclear runaway (TNR)
on the surface of a white dwarf in a semi-detached binary system. In the
course of the eruption some
of material is ejected, at
,
and enriched in CNO and other elements as a result of the TNR.
At infrared wavelengths the eruption evolves from the 'fireball' phase, followed by the free-free phase. Many novae then go through a phase of dust formation, with carbon, silicate and UIR-emitting material often present. As the ejected material thins out and the hot stellar remnant continues to evolve, novae go through a nebular phase and, in some cases a coronal line phase.
Novae were first observed in outburst by IRAS in 1983 and a number of these were re-observed by ISO, using the 12, 25, 60 and 100 micron 'IRAS' filters. We have used the CLOUDY code to model the evolution of typical novae from outburst, through the free-free, dust-forming, nebular and coronal phases. We can thus track their evolution - in some cases over a period of several decades - on the far infrared two colour diagram (12/25-25/60). We present the results of this analysis - together with ISOPHOT (PHT-P) data - for 'CO' novae and for 'ONeMg' novae.
We also present PHT-S spectra of old novae.