Tracing Planetary Accretion in a 3 Gyr-old Hydrogen-Rich White Dwarf: The Extremely Polluted Atmosphere of LSPM J0207+3331

Abstract

We report the detection of 13 heavy elements (Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Sr) in the photosphere of LSPM J0207+3331, a ~3 Gyr old hydrogen-rich white dwarf with an effective temperature comparable to that of the Sun. Upper limits on carbon, obtained through the absence of molecular CH, suggest accretion from a carbon-volatile-depleted source. The accreted parent body exhibits slight deficits of Mg and Si relative to Fe but otherwise bulk Earth-like abundance patterns; a reasonable interpretation is that LSPM J0207+3331 is accreting a massive differentiated rocky body that had a core mass fraction higher than the Earth's. The high level of pollution indicates that substantial accretion events can still occur even after 3 Gyr of cooling. We also detect weak Ca II H & K line-core emission, making this only the second known isolated polluted white dwarf to exhibit this phenomenon and suggesting the presence of additional physical processes in or above the upper atmosphere. Our analysis also highlights the critical importance of including heavy elements in the model atmosphere structure calculations for highly polluted hydrogen-rich white dwarfs. Neglecting their contribution significantly impacts the inferred thermodynamic structure, leading to inaccuracies in derived stellar parameters. Finally, we show that the observed 11.3 microns infrared excess can be explained by a single silicate dust disk rather than a two-ring disk model.

19 pages, 11 figures. Accepted for publication in ApJ on September 22, 2025

References in corpus (28)

• Mass-Radius Relationships for Solid Exoplanets
• The frequency of planetary debris around young white dwarfs
• Monte Carlo radiative transfer in protoplanetary disks
• A gaseous metal disk around a white dwarf
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• The Chemical Composition of an Extrasolar Minor Planet
• Stellar Abundances in the Solar Neighborhood: The Hypatia Catalog
• On the Spectral Evolution of Cool, Helium-Atmosphere White Dwarfs: Detailed Spectroscopic and Photometric Analysis of DZ Stars
• The Chemical Composition of an Extrasolar Kuiper-Belt-Object
• Oxygen fugacities of extrasolar rocks: Evidence for an Earth-like geochemistry of exoplanets
• The Elemental Abundances (with Uncertainties) of the Most Earth-like Planet
• The frequency of gaseous debris discs around white dwarfs
• Convective Overshoot and Macroscopic Diffusion in Pure-Hydrogen Atmosphere White Dwarfs
• Gaia Data Release 3: Chemical cartography of the Milky Way
• A white dwarf accreting planetary material determined from X-ray observations
• Planetary Systems Around White Dwarfs
• Horizontal spreading of planetary debris accreted by white dwarfs
• A dearth of small particles in the transiting material around the white dwarf WD 1145+017
• A 3 Gyr White Dwarf with Warm Dust Discovered via the Backyard Worlds: Planet 9 Citizen Science Project
• No evidence for a strong decrease of planetesimal accretion in old white dwarfs
• Infrared Excesses around Bright White Dwarfs from Gaia and unWISE. II
• New chondritic bodies identified in eight oxygen-bearing white dwarfs
• The Geometry of the G29-38 White Dwarf Dust Disk from Radiative Transfer Modeling
• How the origin of stars in the Galaxy impacts the composition of planetary building blocks
• Asynchronous accretion can mimic diverse white dwarf pollutants II: water content
• A cool, magnetic white dwarf accreting planetary debris
• XMM-Newton Detection of X-ray Emission from the Metal-Polluted White Dwarf G 29-38
• Characterizing planetary material accreted by cool helium atmosphere white dwarfs using an exponentially decaying disc model

Cited by in corpus (1)

• I Can Do It With A Broken Planetesimal: Characterising the planetary debris in heavily polluted cool white dwarfs