Revisiting the Chemical Composition of WD 1145+017: Impact of Circumstellar Disk Contamination on Photospheric Abundances

Abstract

We performed a chemical analysis of the asteroid-bearing white dwarf WD 1145+017 using optical and ultraviolet spectroscopic data from 25 epochs between 2015 and 2023. We present an updated gas disk model with improved opacity calculations and temperature profiles to properly account for all circumstellar absorption features. Incorporating these changes into our models, we identified at least 11 elements in the disk, including a detection of circumstellar Na. We detected 16 elements in the photosphere, including new detections of P, Co, and Cu. At 16 elements, WD 1145+017 ties GD 362 as one of the most polluted white dwarfs in terms of the number of elements detected. We find that both the disk and photosphere compositions align, to first order, with CI Chondrite. Our study underscores the importance of accounting for circumstellar absorption, as neglecting them leads to significant abundance errors. Additionally, the analysis of the disk’s opacity highlighted an ultraviolet flux reduction due to a pseudo-continuum due to an optically thick component. This result may affect previous analyses of other polluted white dwarfs, suggesting a need for revisiting some studies.

Keywords

• White dwarf stars
• Ultraviolet spectroscopy
• Circumstellar gas
• Planetesimals
• Extrasolar rocky planets