Classical Novae In Outburst Research Articles

SwiftX‐Ray Observations of Classical Novae

The new γ-ray burst (GRB) mission Swift has obtained pointed observations of several classical novae in outburst. We analyzed all the observations of classical novae from the Swift archive up to 2006 June 30. We analyzed usable observations of 12 classical novae and found 4 nondetections, 3 weak sources, and 5 strong sources. This includes detections of two novae exhibiting spectra resembling those of supersoft X-ray binary source spectra (SSS), implying ongoing nuclear burning on the white dwarf surface. With these new Swift data, we add to the growing statistics of the X-ray duration and characteristics of classical novae.

Classical novae in outburst: evolution of the ultraviolet emission lines in CO novae

A comparative study is made of the temporal changes of the ionization level in seven CO novae well monitored with the IUE satellite at low resolution. The investigation is based on the evolution of the fluxes in eight strong ultraviolet emission lines covering a wide range of ionization potentials, from Mg  (7.6 eV) to N  (77.5 eV). We find that the rate of increase of the ionization conditions in the emitting regions is uniform in the sample of novae considered, provided the time scale is normalized to the optical decay time t3. The implications of this result for the nova ejected masses and for the nuclear turnoff time are discussed.

Classical novae in outburst: The early evolution of the ultraviolet continuum

In the framework of a phenomenological study of the ultraviolet properties of classical novae in outburst, we have selected 12 objects among the best monitored at low resolution with the IUE satellite, and studied the temporal evolution of the ultraviolet continuum and of the O i 1300 A line flux during the early post{outburst phase. We conrm that the UV flux maximum takes place systematically after the visual maximum and that its time delay is a linear function of t3. A linear dependence on t3 is also found for the duration of the UV outburst and for the time the O i line flux reaches a maximum. This latter time marks the start of the transition phase to nebular conditions. Within the uncertainties imposed by the sample of objects used and by the observational errors, these results suggest a quite homogeneous behaviour of classical novae in the ultraviolet range.

Ultraviolet Observations of Classical Novae in Outburst

More than a dozen classical novae in outburst have been observed with the International Ultraviolet Explorer since its launch in 1978. These data represent a crucial breakthrough in understanding several aspects of the classical novae phenomenon including nucleosynthesis, the energetics of the explosion, the dynamics of the mass ejection, and the processes of dust formation. Also they are important to gain insight on the nature of the white dwarf components and then on the evolutionary scenario of these binary systems.The UV emission lines include important transitions from several species such as He, C, N and O, Ne, Mg, and Al which, whenever symultaneous optical data were available, have lead to a detailed knowledge of the physical conditions in the nebular phases and to the determination, with unprecedented accuracy, of the chemical abundances in the ejecta (see e.g.: Stickland et al. 1981; Williams et al. 1985; Snijders et al. 1987). Precise abundance determinations provide crucial constraints on nucleosinthesis during TNR as well as on the efficiency of diffusion and mixing processes. The ultraviolet range provides also effective means to determine the value of the reddening from the strength of the 2200 A dust feature or from the emission line ratios; an accurate determination of this parameter from the UV is essential, for example, to determine the energy budget of novae and the temperature of the remnants.

Soft X-Ray Emission from Classical Novae in Outburst

AbstractTheoretical modeling of novae in outburst predicts that they should be active emitters of radiation at soft X-ray wavelengths twice during their outburst. The first time occurs very early in the outburst when only a very sensitive all sky survey will be able to detect them. This period lasts only a few hours for the very fastest novae. They again become bright in X-rays late in the outburst when the remnant object becomes very hot and is still luminous. Both simulations and observations show that novae can remain very hot for months to years. It is important to observe them at these late times because a measurement both of the flux and temperature can provide information about the mass of the white dwarf, the turn-off time scale, and the energy budget of the outburst.

Optical Studies of Classical Novae in Outburst

AbstractA nova is followed optically from preoutburst to postoutburst appearance. Photospheric and atmospheric observational data are explained qualitatively through the energy budget, apparent in super-Eddington, Eddington, and sub-Eddington states, and the particle fluxes, according to their role in Grotrian’s model. In some instances, interpretations connected with Grotrian’s model are compared to results based on hydrostatic atmosphere models, for which quantitative versions exist. It is hoped that the physically and observationally sound ‘Ansatz’ of Grotrian may find followers to formulate an updated and extended theory.