Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

High Velocity Circumstellar Gas Orbiting a White Dwarf Star

B. Zuckerman, Érika Le Bourdais, Beth L. Klein, Patrick Dufour, Carl Melis, Alycia J. Weinberger, Siyi Xu, Antoine Bédard, Detlev Koester

Abstract

Numerous white dwarf stars are known to be orbited by disks of gas and dust. To date, broad, about 300 km s-1 wide, gaseous circumstellar absorption features have only been reported for the already iconic WD 1145+017, where one is witnessing the breakup of an extrasolar asteroid in real time. We report here the discovery of absorption from circumstellar gas around a second white dwarf (WD J0234-0406) with similarly broad features. The observed lines are carried by ions of Ca, Cr, Fe, Ti, Mg, Mn, Na, O, Si, Sc, Sr, Ti, and V. In addition, deep, non-photospheric lines of Si IV are seen in the ultraviolet; we compare these with Si IV lines previously seen in the ultraviolet spectra of various other white dwarfs. The apparent broadband flux of WD 1145+017 is known to change often and rapidly as chunks of the asteroid pass between the star and Earth. No such variations are seen in the brightness of WD J0234-0406. In addition, while the strength/structure of circumstellar absorption features at WD 1145+017 has changed dramatically with time, nothing similar is seen at WD J0234-0406. Excess infrared emission at WD J0234-0406 indicates the presence of circumstellar dust particles.

High Velocity Circumstellar Gas Orbiting a White Dwarf Star

Abstract

Numerous white dwarf stars are known to be orbited by disks of gas and dust. To date, broad, about 300 km s-1 wide, gaseous circumstellar absorption features have only been reported for the already iconic WD 1145+017, where one is witnessing the breakup of an extrasolar asteroid in real time. We report here the discovery of absorption from circumstellar gas around a second white dwarf (WD J0234-0406) with similarly broad features. The observed lines are carried by ions of Ca, Cr, Fe, Ti, Mg, Mn, Na, O, Si, Sc, Sr, Ti, and V. In addition, deep, non-photospheric lines of Si IV are seen in the ultraviolet; we compare these with Si IV lines previously seen in the ultraviolet spectra of various other white dwarfs. The apparent broadband flux of WD 1145+017 is known to change often and rapidly as chunks of the asteroid pass between the star and Earth. No such variations are seen in the brightness of WD J0234-0406. In addition, while the strength/structure of circumstellar absorption features at WD 1145+017 has changed dramatically with time, nothing similar is seen at WD J0234-0406. Excess infrared emission at WD J0234-0406 indicates the presence of circumstellar dust particles.
Paper Structure (20 sections, 16 figures)

This paper contains 20 sections, 16 figures.

Table of Contents

  1. Introduction
  2. OBSERVATIONS AND DATA REDUCTION
  3. Kast Spectroscopy
  4. HIRES Spectroscopy
  5. MagE Spectroscopy
  6. Cosmic Origins Spectrograph Spectroscopy
  7. Zwicky Transient Facility Photometry
  8. METHODS AND MODELS
  9. Photometric Parameters
  10. Gas Disk Model and Photospheric Abundances
  11. RESULTS
  12. Secular Variability
  13. Gaseous Circumstellar Features
  14. Photospheric Spectrum and Stellar Classification
  15. Parent Body Composition and Mass
  16. ...and 5 more sections

Figures (16)

  • Figure 1: Photometric/spectroscopic fit to WD J0234-0406. Left panel: photometric fit (open circles) on SDSS ugriz data (error bars). Right panel : Best fit model (red) over the Kast spectrum.
  • Figure 2: Spectral energy distribution of WD J0234-0406. Photometric data from GALEX bianchi_revised_2017, SDSS alam_eleventh_2015, Pan-STARRS flewelling_pan-starrs1_2020, Two Micron All Sky Survey cutri_2mass_2003, VISTA Hemisphere Survey (mcmahon_first_2013, and CatWISE eisenhardt_catwise_2020 surveys. Spitzer data are from lai_infrared_2021.
  • Figure 3: ZTF r$'$ lightcurve for WD J0234-0406. The star appears to be stable with no obvious transit events or variability. Most spectroscopic observations reported in this paper were performed throughout the first half of the displayed lightcurve time range.
  • Figure 4: WD J0234-0406 (black) vs the featureless white dwarf calibration star EGGR 180 (red). The deep narrow features are photospheric. The shallower, broader, features are circumstellar. Identification of a few prominent lines: 3349.03 and 3349.40 doublet, 3361.21, and 3272.79 Ti2. 3368.04 Cr2. 3380.11 Fe1. 3390 - 3396 is a blend of lines (see Table \ref{['tab4:simple']}).
  • Figure 5: Spectral region dominated by circumstellar absorption features.
  • ...and 11 more figures