Limits on Planets Around White Dwarf Stars

TL;DR

This paper investigates the presence of planetary companions around pulsating white dwarf stars by analyzing pulsation timing variations, setting limits on companion masses, and identifying a candidate planet around one star.

Contribution

It introduces a method to detect planets via pulsation timing variations and reports the first candidate planet around a white dwarf star using this technique.

Findings

Limits on planets greater than a few Jupiter masses around 15 white dwarfs.

Detection of a timing variation consistent with a 2 M_J planet in a 4.5-year orbit.

Discussion of alternative explanations for the observed signal.

Abstract

We present limits on planetary companions to pulsating white dwarf stars. A subset of these stars exhibit extreme stability in the period and phase of some of their pulsation modes; a planet can be detected around such a star by searching for periodic variations in the arrival time of these pulsations. We present limits on companions greater than a few Jupiter masses around a sample of 15 white dwarf stars as part of an on-going survey. One star shows a variation in arrival time consistent with a 2 M_J planet in a 4.5 year orbit. We discuss other possible explanations for the observed signal and conclude that a planet is the most plausible explanation based on the data available.