The gaseous debris disk of the white dwarf SDSS J1228+1040. HST/COS search for far-ultraviolet signatures

Abstract

Gaseous and dust debris disks around white dwarfs (WDs) are formed from tidally disrupted planetary bodies. This offers an opportunity to determine the composition of exoplanetary material by measuring element abundances in the accreting WD's atmosphere. A more direct way to do this is through spectral analysis of the disks themselves. Currently, the number of chemical elements detected through disk emission-lines is smaller than that of species detected through lines in the WD atmospheres. We assess the far-ultraviolet (FUV) spectrum of one well-studied object (SDSS J122859.93+104032.9) to search for disk signatures at wavelengths <1050 angstrom, where the broad absorption lines of the Lyman series effectively block the WD photospheric flux. We performed FUV observations (950-1240 angstrom) with the Hubble Space Telescope/Cosmic Origins Spectrograph and used archival optical spectra. We compared them with non-local thermodynamic equilibrium model spectra. In addition, we investigate the Ca II infrared triplet (IRT) line profiles to constrain disk geometry and composition. No disk emission-lines were detected in the FUV spectrum, indicating that the disk effective temperature is about 5000K. The long-time variability of the Ca II IRT was reproduced with a precessing disk model of bulk Earth-like composition, having a surface mass density of 0.3g/cm2 and an extension from 55 to 90 WD radii. The disk has a spiral shape that precesses with a period of approximately 37 years, confirming previous results.

5 pages, 5 figures, accepted for publication in A&A

References in corpus (9)

• The frequency of planetary debris around young white dwarfs
• A gaseous metal disk around a white dwarf
• Pollution of single white dwarfs by accretion of many small asteroids
• Variable Emission from a Gaseous Disc around a Metal-Polluted White Dwarf
• VLT spectroscopy and non-LTE modeling of the C/O-dominated accretion disks in two ultracompact X-ray binaries
• Non-LTE models for the gaseous metal component of circumstellar discs around white dwarfs
• Synthetic NLTE accretion disc spectra for the dwarf nova SS Cyg during an outburst cycle
• Non-LTE spectral models for the gaseous debris-disk component of Ton 345
• Non-LTE modeling of supernova-fallback disks

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• Five New Post-Main-Sequence Debris Disks with Gaseous Emission
• WIRED for EC: New White Dwarfs with $\text{WISE}$ Infrared Excesses and New Classification Schemes from the Edinburgh-Cape Blue Object Survey
• A Characterization of the Circumstellar Gas around WD 1124-293 using Cloudy
• Formation of eccentric gas discs from sublimating or partially disrupted asteroids orbiting white dwarfs
• Modeling the Evolution of Silicate/Volatile Accretion Discs around White Dwarfs
• Disk or Companion: Characterizing Excess Infrared Flux in Seven White Dwarf Systems with Near-Infrared Spectroscopy
• Velocity-imaging the rapidly precessing planetary disc around the white dwarf HE 1349-2305 using Doppler tomography
• Origin of Ca II emission around polluted white dwarfs
• Detecting water ice and vapor disks originating from icy planetary bodies around white dwarfs with future PRIMA observations
• Modeling Circumstellar Gas Emission around a White Dwarf Using Cloudy