Constraints on Remnant Planetary Systems as a Function of Main-Sequence Mass with HST/COS

TL;DR

This study uses HST/COS ultraviolet spectra of young white dwarfs to investigate the presence of remnant planetary systems, revealing a lower occurrence of metal pollution in massive white dwarfs from more massive progenitors.

Contribution

It provides updated measurements of planetary debris around white dwarfs, highlighting how metal pollution varies with white dwarf mass and linking it to planetary formation around intermediate-mass stars.

Findings

Over 40% of white dwarfs show signs of planetary debris.

Metal pollution decreases to about 11% in massive white dwarfs (>0.8 M_sun).

Approximately 44% of lower-mass white dwarfs (<0.7 M_sun) are actively accreting planetary material.

Abstract

As the descendants of stars with masses less than 8 M$_{\odot}$ on the main sequence, white dwarfs provide a unique way to constrain planetary occurrence around intermediate-mass stars (spectral types BAF) that are otherwise difficult to measure with radial-velocity or transit surveys. We update the analysis of more than 250 ultraviolet spectra of hot ($13{,}000$ K $< T_{\mathrm{eff}} <$ $30{,}000$ K), young (less than $800$ Myr) white dwarfs collected by the Hubble Space Telescope, which reveals that more than 40% of all white dwarfs show photospheric silicon and sometimes carbon, signpost for the presence of remnant planetary systems. However, the fraction of white dwarfs with metals significantly decreases for massive white dwarfs (M$_{\rm WD}~>$ 0.8 M$_{\odot}$), descendants of stars with masses greater than 3.5 M$_{\odot}$ on the main sequence, as just $11^{+6}_{-4}$% exhibit metal pollution. In contrast, $44\pm6$% of a subset of white dwarfs (M$\rm _{WD}~<$ 0.7 M$_{\odot}$) unbiased by the effects of radiative levitation are actively accreting planetary debris. While the population of massive white dwarfs is expected to be influenced by the outcome of binary evolution, we do not find merger remnants to broadly affect our sample. We connect our measured occurrence rates of metal pollution on massive white dwarfs to empirical constraints into planetary formation and survival around stars with masses greater than 3.5 M$_{\odot}$ on the main sequence.