The pulsating white dwarf G117-B15A: still the most stable optical clock known

TL;DR

This paper discusses the white dwarf G117-B15A, which has the most stable optical pulsation period, making it an exceptional natural clock useful for testing fundamental physics and searching for external companions.

Contribution

It provides precise measurements of G117-B15A's pulsation period and demonstrates its utility as a stable optical clock for fundamental physics constraints.

Findings

Pulsation period varies by only 5.12×10^{-15} s/s.

No glitches observed in pulsation period.

Can constrain dark matter interactions and substellar companions.

Abstract

The pulsating hydrogen atmosphere white dwarf star G 117-B15A has been observed since 1974. Its main pulsation period at 215.19738823(63) s, observed in optical light curves, varies by only (5.12+/-0.82)x10^{-15} s/s and shows no glitches, as pulsars do. The observed rate of period change corresponds to a change of the pulsation period by 1 s in 6.2 million years. We demonstrate that this exceptional optical clock can continue to put stringent limits on fundamental physics, such as constraints on interaction from hypothetical dark matter particles, as well as to search for the presence of external substellar companions.