Modeling of the Variable Circumstellar Absorption Features of WD 1145+017

TL;DR

This paper develops an eccentric precessing gas disk model to explain the variable circumstellar absorption features of WD 1145+017, providing insights into the gas's physical properties and the disk's precession behavior.

Contribution

The paper introduces a detailed gas disk model that predicts absorption features across wavelengths and phases, improving understanding of circumstellar gas dynamics around white dwarfs.

Findings

Precession period of 4.6±0.3 years successfully matches observed velocity profiles.

Model explains changes in circumstellar feature morphology during transits.

Additional circular rings may be needed to account for certain absorption features.

Abstract

We present an eccentric precessing gas disk model designed to study the variable circumstellar absorption features detected for WD 1145+017, a metal polluted white dwarf with an actively disintegrating asteroid around it. This model, inspired by one recently proposed by Cauley et al., calculates explicitly the gas opacity for any predetermined physical conditions in the disk, predicting the strength and shape of all absorption features, from the UV to the optical, at any given phase of the precession cycle. The successes and failures of this simple model provide valuable insight on the physical characteristics of the gas surrounding the star, notably its composition, temperature and density. This eccentric disk model also highlights the need for supplementary components, most likely circular rings, in order to explain the presence of zero velocity absorption as well as highly ionized Si IV lines. We find that a precession period of $4.6\pm0.3$ yrs can successfully reproduce the shape of the velocity profile observed at most epochs from April 2015 to January 2018, although minor discrepancies at certain times indicate that the assumed geometric configuration may not be optimal yet. Finally, we show that our model can quantitatively explain the change in morphology of the circumstellar features during transiting events.