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A white dwarf bound to the transiting planetary system WASP-98

Southworth, John; Tremblay, Pier-Emmanuel; Gänsicke, Boris T; Evans, Daniel; Močnik, Teo

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Authors

Pier-Emmanuel Tremblay

Boris T Gänsicke

Daniel Evans

Teo Močnik



Abstract

WASP-98 is a planetary system containing a hot Jupiter transiting a late-G dwarf. A fainter star 12? distant has previously been identified as a white dwarf, with a distance and proper motion consistent with a physical association with the planetary system. We present spectroscopy of the white dwarf, with the aim of determining its mass, radius and temperature and hence the age of the system. However, the spectra show the featureless continuum and lack of spectral lines characteristic of the DC class of white dwarfs. We therefore fitted theoretical white dwarf spectra to the ugriz apparent magnitudes and Gaia DR2 parallax of this object in order to determine its physical properties and the age of the system. We find that the system is old, with a lower limit of 3.6 Gyr, but theoretical uncertainties preclude a precise determination of its age. Its kinematics are consistent with membership of the thick disc, but do not allow us to rule out the thin-disc alternative. The old age and low metallicity of the system suggest it is subject to an age-metallicity relation, but analysis of the most metal-rich and metal-poor transiting planetary systems yields only insubstantial evidence of this. We conclude that the study of bound white dwarfs can yield independent ages to planetary systems, but such analysis may be better-suited to DA and DB rather than DC white dwarfs.

Journal Article Type Article
Acceptance Date Aug 3, 2020
Online Publication Date Aug 11, 2020
Publication Date 2020-10
Publicly Available Date Mar 28, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 497
Issue 4
Pages 4416 - 4422
DOI https://doi.org/10.1093/mnras/staa2328
Keywords stars: fundamental parameters, stars: individual: WASP-98, planetary systems, white dwarfs
Publisher URL https://doi.org/10.1093/mnras/staa2328

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