Observations and NLTE Modeling of the Gaseous Planetary Debris Disk around Ton 345

TL;DR

This paper models the gaseous component of a debris disk around white dwarf Ton 345 using non-LTE spectral techniques, aiming to directly determine its chemical composition through emission lines and analyzing observational variability.

Contribution

It introduces non-LTE spectral modeling of gaseous debris disks around white dwarfs and presents new observations of Ton 345 to study line-profile variations.

Findings

Red-violet asymmetry of Ca II triplet nearly disappeared

No significant short-term line-profile variations observed

Spectral modeling provides insights into disk composition

Abstract

Debris disks around single white dwarfs are thought to be the remains of planetary bodies disrupted by tidal forces. Ongoing accretion of the hereby produced dust allows to detect the planetary material in the white dwarf photosphere and to conclude on its chemical composition. As an alternative, the composition can in principle be determined directly from the emission lines of the sometimes additionally observed gaseous component of the disks. To this aim, we perform spectral modeling with our non-LTE code for accretion disks. We have obtained new observations of Ton 345 in order to look for long- and short-term variations in the disk line-profiles. We find that the prominent red-violet asymmetry of the Ca II infrared triplet almost disappeared. Line-profile variations during one night are not seen without doubt.