Connecting circumstellar gas around white dwarfs to small bodies in the solar system
Abstract
There is evidence of circumstellar (CS) material around main sequence (MS), giant, and white dwarf (WD) stars that originates from the small-body population of planetary systems. The detection rates of debris disks around FGK stars range from 18% to 36% and at least 30% of WDs show heavy elements in their atmospheres from accreted planetary dust. For red and asymptotic giant branch stars, mass loss can overwhelm the signature of planetary systems. Linking MS and WD planetary systems remains an objective and challenge, motivated by the question of what happens to this material as its host star evolves off the main sequence, and how do the endpoints of that evolution inform our understanding of the typical chemistry of rocky bodies in planetary systems? One way to address this question is to begin at the end, with the 30% of WDs that have unexpected heavy elements in their photospheres. This "pollution" likely arises from the accretion of planetesimals that were perturbed by outer planet(s) into the WD's tidal radius. These planetesimals survived the evolution of their host stars, and thus inform the chemistry and evolution of the protoplanetary disk and planetary system by which they formed. A small fraction of polluted WDs show either emission or absorption from CS gas, arising from a gas disk produced through the sublimation of a transiting, disintegrating planetesimal. However, models (to date) have not yet been able to link the CS species to the total atomic abundance in gas measured in the photosphere. Here we present self-consistent models of CS gas around various types of WDs and demonstrate how we can determine the abundances of CS absorption lines arising from planetesimals. We build a grid of models and place constraints on the gas masses needed for detection with current observatories, which can be used to constrain the frequency of CS gas around statistical samples of WDs. These models of CS gas around polluted white dwarfs will provide a key to understanding the instantaneous composition of the material flowing from the planetesimals, will guide modeling of the transits and of the dust in these polluted systems, and will help constrain the radial locations of different gas components.
- Publication:
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American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23516104S