Modeling Circumstellar Gas Emission around a White Dwarf Using CLOUDY
Weinberger, Alycia J.; Steele, Amy; Xu, Siyi; Yeh, Sherry; Dufour, P.; Melis, Carl; Klein, Beth L.; Manser, Christopher J.; Dennihy, Erik; Doyle, Alexandra E.; Wang, Tinggui; Rogers, Laura. K.
United States, United Kingdom, Canada, China
Abstract
The chemical composition of an extrasolar planet is fundamental to its formation, evolution, and habitability. In this study, we explore a new way to measure the chemical composition of the building blocks of extrasolar planets by measuring the gas composition of the disrupted planetesimals around white dwarf stars. As a first attempt, we used the photoionization code CLOUDY to model the circumstellar gas emission around white dwarf Gaia J0611‑6931 under some simplified assumptions. We found that most of the emission lines are saturated, and the line ratios approach the ratios of thermal emission; therefore, only lower limits to the number density can be derived. Silicon is the best-constrained element in the circumstellar gas, and we derived a lower limit of 1010.3 cm‑3. In addition, we placed a lower limit on the total amount of gas to be 1.8 × 1019 g. Further study is needed to better constrain the parameters of the gas disk and connect it to other white dwarfs with circumstellar gas absorption.