An Improved Model for the Spectra of Disks of Nova-like Variables

TL;DR

This paper improves spectral modeling of nova-like variable disks by incorporating energy dissipation effects, resulting in spectra that better match observations, especially in the ultraviolet range.

Contribution

It introduces a new spectral model that accounts for energy dissipation in disk atmospheres, aligning theoretical spectra more closely with observed data.

Findings

The model accurately reproduces the spectrum of IX Vel from 1150-6000 Å.

Inclusion of energy dissipation flattens the vertical temperature profile.

The approach resolves previous over-predictions of the Balmer jump depth.

Abstract

The spectra arising from the disks of nova-like variables show many of the features seen in stellar atmospheres. They are typically modelled either from an appropriated weighted set of stellar atmospheres or a disk atmosphere with energy is dissipated near the disk plane, with the effective temperature distribution expected from a steady state accretion disk. However these models generally over-predict the depth of the Balmer jump and the slope of the spectrum in the ultraviolet. The problem is likely due to energy dissipation in the disk atmosphere, which produces a flatter vertical temperature profile than is observed in stars. Here, we provide validation for this hypothesis in the form of spectra generated using the stellar atmosphere code TLUSTY using a parametric prescription for energy dissipation as a function of depth and closely match the spectrum of the nova-like IX Vel over the wavelength range 1150-6000 \AA.