Detection of weak circumstellar gas around the DAZ white dwarf WD 1124-293: Evidence for the accretion of multiple asteroids

J. H. Debes, M. Kilic, F. Faedi, E. L. Shkolnik, M. Lopez-Morales, A. J. Weinberger, C. Slesnick, R. G. West

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Abstract

Single metal-polluted white dwarfs with no dusty disks are believed to be actively accreting metals from a circumstellar disk of gas caused by the destruction of asteroids perturbed by planetary systems. We report, for the first time, the detection of circumstellar Ca II gas in absorption around the DAZ WD 1124-293, which lacks an infrared excess. We constrain the gas to >7 R WD and <32000 AU, and estimate it to be at 54 R WD, well within WD 1124-293's tidal disruption radius. This detection is based on several epochs of spectroscopy around the Ca II H and K lines (λ = 3968 Å, 3933 Å) with the MIKE spectrograph on the Magellan/Clay Telescope at Las Campanas Observatory. We confirm the circumstellar nature of the gas by observing nearby sightlines and finding no evidence for gas from the local interstellar medium. Through archival data we have measured the equivalent width of the two photospheric Ca lines over a period of 11years. We see <5%-7% epoch-to-epoch variation in equivalent widths over this time period, and no evidence for long term trends. The presence of a circumstellar gas implies a near edge-on inclination to the system, thus we place limits to short period transiting planetary companions with R > R using the Wide Angle Search for Planets survey. The presence of gas in orbit around WD 1124-293 implies that most DAZs could harbor planetary systems. Since 25%-30% of white dwarfs show metal line absorption, the dynamical process for perturbing small bodies must be robust.

Original languageEnglish (US)
Article number59
JournalAstrophysical Journal
Volume754
Issue number1
DOIs
StatePublished - Jul 20 2012

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Keywords

  • Circumstellar matter
  • Planetary systems
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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