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

Abstract

As the descendants of stars with masses less than 8 M _⊙ 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 _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, signposts for the presence of remnant planetary systems. However, the fraction of white dwarfs with metals significantly decreases for massive white dwarfs (M _WD > 0.8 M _⊙), descendants of stars with masses greater than 3.5 M _⊙ on the main sequence, as just 11‑4+6 % exhibit metal pollution. In contrast, 44% ± 6% of a subset of white dwarfs (M _WD < 0.7 M _⊙) 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 of planetary formation and survival around stars with masses greater than 3.5 M _⊙ on the main sequence.