Multiwavelength modeling the SED of very slow novae PU Vul and V723 Cas

TL;DR

This study models the spectral energy distribution of very slow novae PU Vul and V723 Cas, revealing a transient decrease in luminosity caused by neutral disk formation and suggesting a mechanism for prolonged high energy output.

Contribution

It introduces a multiwavelength spectral modeling approach to analyze slow novae, uncovering the role of neutral disks and challenging existing theories on nova luminosity evolution.

Findings

Transient luminosity decrease linked to neutral disk formation.

Luminosity recovers after disk disappearance, exceeding Eddington limit.

Mechanism maintaining high energy output is likely powered by the accretor.

Abstract

Evolution in the spectrum of very slow novae PU Vul and V723 Cas during their transition from the optical maximum to the nebular phase is investigated using the method of disentangling the composite UV/optical spectra. Model SEDs suggested that a transient decrease in the WD luminosity, during the decline from the maximum, was caused by a negative beaming effect, when a neutral disk around the WD was formed. When the disk disappeared, the luminosity increased again to values from the beginning of the outburst (in the case of V723 Cas, at/above the Eddington limit). This suggests the presence of a mechanism maintaining a high energy output for a much longer time than it is predicted by the current theories. Similarity of light curves, but enormous difference of the separation between the components of PU Vul and V723 Cas binaries suggest that the mechanism is basically powered by the accretor.