A Circumbinary Planet in Orbit Around the Short-Period White-Dwarf Eclipsing Binary RR Cae

TL;DR

This study reports the detection of a circumbinary giant planet around the white-dwarf eclipsing binary RR Cae, based on eclipse timing variations indicating gravitational influence from the planet and potential evidence for another distant companion.

Contribution

The paper presents the discovery of a circumbinary planet around RR Cae using eclipse timing variations, and suggests the possible existence of a second distant planet based on long-term orbital changes.

Findings

Detected a 11.9-year cyclic variation in eclipse timings.

Estimated the planet's mass as approximately 4.2 Jupiter masses.

Indicated a potential second planet from long-term orbital trends.

Abstract

By using six new determined mid-eclipse times together with those collected from the literature, we found that the Observed-Calculated (O-C) curve of RR Cae shows a cyclic change with a period of 11.9 years and an amplitude of 14.3s, while it undergoes an upward parabolic variation (revealing a long-term period increase at a rate of dP/dt =+4.18(+-0.20)x10^(-12). The cyclic change was analyzed for the light-travel time effect that arises from the gravitational influence of a third companion. The mass of the third body was determined to be M_3*sin i' = 4.2(+-0.4) M_{Jup} suggesting that it is a circumbinary giant planet when its orbital inclination is larger than 17.6 degree. The orbital separation of the circumbinary planet from the central eclipsing binary is about 5.3(+-0.6)AU. The period increase is opposite to the changes caused by angular momentum loss via magnetic braking or/and gravitational radiation, nor can it be explained by the mass transfer between both components because of its detached configuration. These indicate that the observed upward parabolic change is only a part of a long-period (longer than 26.3 years) cyclic variation, which may reveal the presence of another giant circumbinary planet in a wide orbit.