# A far-UV survey of three hot, metal-polluted white dwarf stars: WD0455-282, WD0621-376, and WD2211-495

## TL;DR

This study uses high-resolution UV data from Hubble and archival FUSE data to analyze three hot, metal-polluted white dwarfs, revealing external metal accretion and detecting multi-component circumstellar absorption, a first in such stars.

## Contribution

It provides detailed measurements of stellar parameters and metal abundances, compares them with radiative levitation theory, and reports the first detection of multi-component circumstellar absorption in a white dwarf.

## Key findings

- Observed metal abundances exceed radiative levitation predictions.
- Detected circumstellar absorption with multiple velocity components.
- Confirmed ongoing external metal accretion in the white dwarfs.

## Abstract

Using newly obtained high-resolution data ($R\sim{1\times{10}^{5}}$) from the \textit{Hubble Space Telescope}, and archival UV data from the \textit{Far Ultraviolet Spectroscopic Explorer} we have conducted a detailed UV survey of the three hot, metal-polluted white dwarfs WD0455-282, WD0621-376, and WD2211-495. Using bespoke model atmospheres we measured $T_{\mathrm{eff}}$, log $g$, and photospheric abundances for these stars. In conjunction with data from Gaia we measured masses, radii, and gravitational redshift velocities for our sample of objects. We compared the measured photospheric abundances with those predicted by radiative levitation theory, and found that the observed Si abundances in all three white dwarfs, and the observed Fe abundances in WD0621-376 and WD2211-495, were larger than those predicted by an order of magnitude. These findings imply not only an external origin for the metals, but also ongoing accretion, as the metals not supported by radiative levitation would sink on extremely short timescales. We measured the radial velocities of several absorption features along the line of sight to the three objects in our sample, allowing us to determine the velocities of the photospheric and interstellar components along the line of sight for each star. Interestingly, we made detections of circumstellar absorption along the line of sight to WD0455-282 with three velocity components. To our knowledge, this is the first such detection of multi-component circumstellar absorption along the line of sight to a white dwarf.